Assessment of Aircraft Noise in Hackett, ACT
AVU 00509
for
Chief Minister’s Department
ACT Government
by
Marion Burgess BSc (Hons) MSc (Acoust), FAAS
and Matthew McCarty BE (Hons) ME
Acoustics & Vibration Unit
School of Engineering and Information Technology
UNSW at ADFA
30 March 2010
Any use of the Report, use of any part of it or use of the names University of New South Wales
and UNSW, the name of any unit of the University or the name of the consultant in direct or in
indirect advertising or publicity is forbidden.
Assessment of Aircraft Noise in Hackett, ACT
AVU 00509
for Chief Minister’s Department, ACT Government
CONTENTS
GLOSSARY OF TERMS RELATING TO AIRCRAFT OPERATIONS AND NOISE.. 1
EXECUTIVE SUMMARY ........................................................................................... 5
SUMMARY OF FINDINGS....................................................................................... 10
1.
INTRODUCTION .............................................................................................. 13
2.
AIRCRAFT OPERATIONS AT CANBERRA AIRPORT................................... 14
2.1.
AIRCRAFT FLIGHT PATHS ...................................................................... 14
2.1.
CANBERRA AIRPORT NOISE MODELLING............................................ 15
2.2.
CANBERRA AIRPORT NOISE ABATEMENT PROCEDURES ................. 19
2.3.
ADDITIONAL ACTIONS TO MINIMISE AIRCRAFT NOISE IMPACT IN
NORTH CANBERRA ............................................................................................ 20
2.4.
STANDARD DEPARTURE PROCEDURES FOR AIRCRAFT UNDER
INSTRUMENT FLIGHT RULES ........................................................................... 22
3.
2.5.
GA AIRCRAFT PROCEDURES ................................................................ 25
2.6.
SUMMARY ................................................................................................ 29
CONCERNS OF RESIDENTS OF NORTH CANBERRA ................................. 30
3.1.
4.
SUMMARY ................................................................................................ 31
MEASUREMENT AND ANALYSIS OF AIRCRAFT NOISE IN HACKETT ...... 32
4.1.
NOISE AND FLIGHT PATH MONITORING............................................... 32
4.2.
SET UP OF THE MONITOR...................................................................... 34
4.3.
CORRELATED NOISE EVENTS ............................................................... 35
4.4.
WEBTRAK ................................................................................................. 40
4.5.
NOISE EVENT DETAILS........................................................................... 41
4.6.
NON AIRCRAFT NOISE LEVELS ............................................................. 52
4.7.
5.
SUMMARY ................................................................................................ 54
NOISE LEVELS FOR REGULAR PUBLIC TRANSPORT AIRCRAFT ............ 55
5.1.
GENERAL.................................................................................................. 55
5.2.
FREQUENCY OF RPT AIRCRAFT NOISE EVENTS ................................ 56
5.3.
WORST-CASE RPT AIRCRAFT NOISE EVENTS .................................... 59
5.4.
NOISE LEVELS FOR RPT AIRCRAFT EVENTS ON SPECIFIC DAYS.... 64
5.4.1. Typical Weekday in First Quarter ........................................................... 64
5.4.2. Noisy Weekday in First Quarter ............................................................. 66
5.4.3. Typical Weekend day in First Quarter .................................................... 71
5.4.4. Busy Weekday in Second Quarter ......................................................... 75
5.4.5. High Noise Level Day in Second Quarter............................................... 82
5.4.6. Comparison with Data from NMT near a Major Airport........................... 84
5.5.
6.
SUMMARY FOR RPT AIRCRAFT NOISE EVENTS.................................. 86
NOISE LEVELS FOR GENERAL AVIATION AIRCRAFT................................ 89
6.1.
GENERAL.................................................................................................. 89
6.2.
FREQUENCY OF GA AIRCRAFT EVENTS .............................................. 90
6.3.
NOISE LEVELS FOR GA AIRCRAFT EVENTS OVER THE DAY............. 93
6.4.
SPECIFIC GA AIRCRAFT NOISE EVENTS.............................................. 96
6.4.1. Helicopter overflights.............................................................................. 96
6.4.2. Incorrect noise level for GA aircraft overflight....................................... 100
6.5.
SUMMARY FOR GA AIRCRAFT NOISE EVENTS.................................. 102
7.
AIRSERVICES AUSTRALIA QUARTERLY REPORT FOR CANBERRA ..... 104
8.
AIRCRAFT NOISE IMPACT........................................................................... 108
9.
CONCLUDING SUMMARY ............................................................................ 111
10. REFERENCES ............................................................................................... 115
Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
GLOSSARY OF TERMS RELATING TO AIRCRAFT OPERATIONS
AND NOISE
The following provides a brief explanation of some of the terms and acronyms used
in the industry to describe both aircraft noise and aircraft operations:
Altitude
elevation above a known level (see AMSL and AGL).
AGL
‘above ground level’ and is the altitude of an aircraft relative to the
local ground level.
AMSL
‘above mean sea level’ and is the altitude of an aircraft relative to
mean sea level.
AsA
Airservices Australia, which is a government-owned corporation
providing safe and environmentally sound air traffic control management and related
airside services to the aviation industry.
dB
Unit for sound pressure level.
dB(A)
Unit for sound pressure level when an A-weighted frequency filter is
included in the measurement chain.
This A weighting has a similar frequency
response to that of human hearing
Correlation Circle an arbitrary circle around an NMT which is used to identify if an
aircraft was in the vicinity for each noise event. When this is the case, the event is
defined as a ‘correlated noise event’.
Flight Track
representation of an aircraft’s route over the ground, plotted on a
map
General Aviation (GA)
operations
are
those
which
are
not
scheduled
commercial airline activity. This may include charter operators, aero medical
operators, agricultural aviation businesses, aviation-based fire-fighting services,
training and aerial work such as aerial photography etc. It also includes private,
business, recreational and sports aviation activity and supporting businesses such
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
as maintenance providers [from www.infrastructure.gov.au/aviation/general/]. GA
aircraft generally operate under Visual Flight Rules.
Instrument Flight Rules (IFR)
are procedures for flying aircraft using only the
instrument panel for navigation. Most scheduled flights operate under IFR.
Lmax
the maximum sound pressure level during a noise event expressed
in decibels.
Lnight
the A-weighted long-term average sound level determined over all
the 8 hour night periods of a year expressed in decibels. Night period is commonly
taken as from 2201 to 0600 hrs.
Noise and Flight Path Monitoring System (NFPMS)
is managed by AsA
Australia and is the world's largest, most geographically-spread system of its type. It
collects noise data from monitoring terminals around airports and flight path data
from secondary surveillance radar at each airport. It records the identity, flight path
and altitude of each aircraft operating to and from the airport, the noise levels
attributed to individual aircraft that are within the correlation circle, weather data, and
the general background noise. AsA provides summary reports each quarter using
NFPMS data for Brisbane, Cairns, Canberra, Coolangatta, Sydney, Melbourne,
Essendon, Adelaide and Perth airports.
Noise Monitoring Terminal (NMT)
comprises a microphone and a data logger
which continuously transmits to the central computer of the NFPMS. The terminal at
Hackett is a portable terminal as opposed to the fixed terminal at Jerrabomberra.
Noise event
is identified from the NMT data only if it satisfies the criteria that
have been set for that location. A ‘correlated noise event’ is one for which an aircraft
has been identified as being within a ‘correlation circle’. The parameters that are
used to define a noise event include:
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Threshold - the trigger level above which the noise data is considered possibly
due to an aircraft
Minimum rate of increase of the noise levels for the potential aircraft noise
event.
Maximum rate of increase of the noise levels for the potential aircraft noise
event.
Minimum rate of decrease of the noise levels after the maximum level of the
event has passed.
Maximum rate of decrease of the noise levels after the maximum level of
the event has passed.
Pre-trigger measurement which allows for analysis of the data for some time
before the maximum level has been identified.
Post-trigger measurement which allows for analysis of the data for some time
after the maximum level has been identified.
Noise profile
a time record of the noise level recorded by the NMT for a noise
event.
N70
Number of aircraft noise events with Lmax greater than 70 dB(A).
Regular Public Transport Aircraft (RPT aircraft)
aircraft that are scheduled to
occur on a regular basis at fixed times or frequencies on fixed routes [from SECT
194 Transport Act 1983]. RPT aircraft by routine carry out a ‘Standard Instrument
Departure’ and a ‘Standard Terminal Arrival Route’ as they operate under
‘Instrument Flight Rules’.
Standard Instrument Departure (SID): specified tracks and levels that aircraft use
to depart the terminal area. SIDs are designed in accordance with the established
environmental criteria for the location and are individually assessed for their
environmental impact [from www.newparallelrunway.com.au].
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Standard Terminal Arrival Route (STAR): specified tracks and levels that aircraft
use to arrive in the terminal area. STARs are designed in accordance with the
established environmental criteria for the location and are individually assessed for
their environmental impact [from www.newparallelrunway.com.au].
Visual Flight Rules (VFR) are a set of aviation regulations under which a pilot may
operate an aircraft, if weather conditions are sufficient to allow the pilot to visually
control the aircraft’s attitude, navigate and maintain separation from obstacles such
as terrain and other aircraft [from www.newparallelrunway.com.au].
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
EXECUTIVE SUMMARY
The extent of noise impact on the northern suburbs of Canberra from Canberra
Airport operations has been a concern for the local residents. In response to these
concerns, Airservices Australia (AsA) installed a noise monitoring terminal (NMT) in
the suburb of Hackett to obtain quantitative data on the extent of the aircraft noise
impact for the region. The Acoustics and Vibration Unit of the University of New
South Wales at the Australian Defence Force Academy (UNSW@ADFA) was
appointed by the ACT Chief Minister’s Department to undertake an independent
assessment of the data from this NMT. This report provides the findings from the
assessment of data for regular public transport (RPT) and general aviation (GA)
aircraft noise events and compares the findings with those published in the AsA
quarterly report for the first 6 months of the installation at Hackett. Discussion on the
broader aspects of aircraft noise and its assessment are outside the scope
Aircraft operations
Both RPT and GA aircraft operate at Canberra Airport. The standard operating
procedures, noise abatement procedures and additional measures implemented by
the airport aim to minimise overflights of residential areas. Only occasionally due to
safety factors do RPT aircraft fly close to the residential area of Hackett. GA aircraft
are within air traffic control while they are near the suburban areas of North
Canberra but can overfly the northern suburbs and inner suburbs of Canberra.
Concerns about aircraft noise
There have been complaints about excessive aircraft noise from some residents in
North Canberra and in particular from those in Hackett and Watson. The residents
are particularly concerned about sleep disturbance from night time operations and
seek a formal night time curfew to be applied. A noise monitoring terminal (NMT)
was installed by AsA at Hackett in late December 2008 and the data for the first and
second quarters of 2009 has been published by AsA and has been examined by the
Acoustics and Vibration Unit (AVU).
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Noise monitoring terminal
The identification of a noise event with an aircraft relies on the noise event meeting
the parameters set for the NMT and an aircraft being within a correlation circle
around the NMT. The installation at Hackett is challenging as the noise levels for
many aircraft events are similar to those for local noises. The initial analysis by the
AVU showed many cases of incorrectly attributed aircraft noise events and valid
aircraft noise events that were not correlated. Adjustments were made by AsA to the
settings and the correlation circle to try to overcome some of these problems.
Techniques were developed by the AVU to remove some clearly incorrect data.
However, the large correlation circle means that the data sets still include many
incorrectly attributed aircraft noise events. The noise level profile and flight path
would need to be examined for every correlated noise event to fully remove the
incorrect data.
Regular Public Transport (RPT)
The initial analysis of the data for noise events for RPT aircraft involved removal of
multiple events from the data set. Further investigation indicated that the data still
contained incorrectly attributed noise events. As it was not practical to fully remove
all these ‘false positives’, or those with incorrect noise levels and samples of the data
were selected for detailed examination. These included:
a typical weekday;
a typical weekend day;
a day with the greatest number of apparently correlated noise events greater
than 70 dB(A) (a noisy weekday); and
cases of ‘worst case’ RPT aircraft noise events.
Examples of ‘worst case’ noise levels for RPT aircraft were found from three flights
which did not comply with the standard departures due to adverse conditions and
flew directly over the NMT in Hackett. The Lmax values for these overflights ranged
from 66 to 76 dB(A). An extreme ‘worst case’ with Lmax values ranging from 82 to
90 dB(A) occurred for F-18 overflights as part of the celebrations for Australia Day.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
The detailed analysis for the four loudest event on a day that had the largest number
of higher noise events showed that the levels for the noise events with Lmax greater
than 66 dB(A) had been incorrectly attributed to aircraft. While there still remains
some doubt about the correct attribution of noise levels to RPT aircraft, the analysis
indicates that the noise levels at Hackett due to standard RPT aircraft departures
can be between 55 and 65 dB(A). It should be noted that there are many community
noise events with even higher noise levels during the day and evenings.
General Aviation
General Aviation (GA) aircraft are under direction from air traffic control in the
controlled airspace around the airport that extends beyond the Hackett area. They
are not required to follow the published standard departure procedures but are
directed by air traffic control while carrying out their desired operation (e.g. circuits,
city scenic flights). While GA aircraft are routed as much as possible over the non­
residential areas they do overfly the northern suburban areas of Canberra.
After removing clear duplicate events from the correlated noise event data there
were 420 apparently correlated noise events over a 73 day period for the GA aircraft
data set with the smaller correlation circle and so less incorrect data. Most GA
aircraft operate only during daylight hours and there were no correlated noise events
during the night. The number of potentially correlated noise events was greater
during the weekends and distributed throughout the daytime hours rather than
occurring during morning and evening peak as was the case for RPT aircraft noise
events. As it was not practical to investigate the detail of every noise event to check
correct attribution, detailed analysis was undertaken for:
a busy weekday
a busy weekend
selected events including those related to helicopters
While there still remains some doubt about the correct attribution of noise levels to
GA aircraft, the analysis indicates that frequency of the noise levels at Hackett due
to GA aircraft can be less than 2.4 events per day between 60 and 65 dB(A), less
than 0.6 events between 65 and 70 dB(A) and less than 0.3 events between 70 and
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
75 dB(A). It should be noted that there is a greater incidence of non-aircraft noise
events with even higher noise levels during the day and evenings.
Airservices Australia Quarterly Report
The AsA Quarterly Reports for the periods January - March 2009 and April to June
2009 include the data summaries and analysis by AsA for the NMT at Hackett. The
reports acknowledge the likelihood of community noise events being incorrectly
attributed to aircraft. In their analysis AsA has removed some incorrect data and
conclude that the number of aircraft noise events greater than 70 dB(A) (N70) was at
least 0.44 and 0.56 events per day for the first and second quarters respectively.
From the detailed analysis of sub samples of the data set by the AVU, and as
discussed in the previous sections of this report, it appears that these are
overestimates for the N70. The AVU analysis has shown that RPT aircraft noise
N70 only occur occasionally when there is non compliance with noise abatement
procedures. Such direct flyovers of the residential areas are usually due to safety
issues or for special event celebrations.
The AVU analysis for GA aircraft has
indicated a N70 of less than 0.3 events per day.
The listing of mean Lmax aircraft noise levels for each aircraft type shows only two
GA aircraft types with levels just over 65 dB(A). AVU analysis has shown that the
mean values include data for incorrectly attributed aircraft and after reanalysis all the
mean Lmax aircraft noise levels are less than 65dB(A).
Aircraft noise impact
A major concern of the Hackett residents is that increased night time aircraft
operations would lead to excessive noise intrusion and sleep disturbance and there
are no clear criteria nationally or internationally.
The guideline from Australian
Standard 2021 [2000] is that the Lmax, inside the bedroom should not exceed
50 dB(A). An average value of attenuation for a residential building depends on the
construction but can be assumed to be between 15 and 25 dB for open and closed
windows respectively. Thus an outside Lmax of 65 to 75 dB(A) could be expected to
be reduced to 50 dB(A) inside for open and closed windows respectively.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
The World Health Organisation (WHO) recommendations for community noise levels
[World Health Organisation 1999] included a table listing guidelines for a number of
specific environments. The guideline for Lmax inside bedrooms of 45 dB(A)can be
compared with the Australian Standard 2021 [2000] value of 50 dB(A).
The
corresponding outside guideline of 60 dB(A) is based on assumed 15 dB reduction
by the building enclosure with windows open.
The recent WHO document on “Night Noise Guidelines For Europe” [World Health
Organisation 2009]. This proposes guidelines based on the health effects of night
time noise which are not given in terms of Lmax but in terms of the noise level
averaged over the night. The guideline and target levels assuming open windows,
for Lnight, outside are 40 and 55 dB(A) respectively. The AsA data shows that the current
Lnight,outside at the NMT is around 42 dB(A). Simple modelling shows that it would
need over 100 and 500 aircraft during the night each with Lmax of 65 dB(A) to
increase the Lnight, outside to 50 and 55 dB(A) respectively.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
SUMMARY OF FINDINGS
The extent of noise impact on the northern suburbs of Canberra from Canberra
Airport operations has been a concern for the local residents. Following are some
of the findings from the study of the data from the first six months of the
installation of the Noise Monitoring Terminal at Hackett.
Aircraft operations
• Standard operating procedures, noise abatement procedures and additional
measures implemented by the airport aim to minimise overflights of
residential areas.
• Only in exceptional circumstances, such as when extreme weather events
require diversions, do RPT aircraft overfly or fly close to the residential area
of Hackett.
• GA aircraft are within air traffic control while they are near the suburban
areas of North Canberra but do frequently overfly residential areas.
Concerns about aircraft noise
• There are ongoing complaints about excessive aircraft noise from residents
in North Canberra and in particular from some in Hackett and Watson
• Of particular concern is sleep disturbance from night time operations and a
formal night time curfew is sought.
Noise monitoring terminal
• The noise monitor was appropriately located near the Mt Ainslie-Mt Majura
saddle and with respect to the topography for the area. It is unlikely that
there would be any significant ‘shadowing’ effect on the maximum aircraft
noise levels.
• The residential areas are approximately 2800m from the extended centreline
of the main runway which means that the noise levels for most RPT aircraft
events are similar to those for local noises.
• Initial analysis by the AVU showed many cases of incorrectly attributed
aircraft noise events and aircraft noise levels as well as missed events
• Implementation of a larger, non-standard correlation circle, set by AsA to
identify when an aircraft is in the vicinity of the noise monitor, reduces the
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
incidence of missed aircraft noise events but increases incorrect attribution
of noise events to aircraft.
• To confirm correct attribution to an aircraft, every noise event would need to
be examined individually.
Regular Public Transport (RPT)
• The highest Lmax noise levels from RPT aircraft, which occurred when
aircraft flew right over Hackett for safety because of extreme weather, were
66 to 76 dB(A).
Lmax for F-18 military jet overflights for Australia Day
celebration were 82 to 90 dB(A). Both of these types of aircraft operations
are infrequent.
• Standard RPT aircraft departures can have Lmax between 55 and 65 dB(A).
• Of those sampled, no valid RPT events were found greater than 66 dB(A)
General Aviation
• GA aircraft do frequently fly over Hackett during the day but only rarely at
night (between 22:00 and 06:00 hrs)
• Estimate of incidence of Lmax for GA aircraft
�
60 and 65 dB(A)
less than 2.4 events per day
�
65 and 70 dB(A)
less than 0.6 events per day
�
70 and 75 dB(A)
less than 0.3 events per day
Airservices Australia Quarterly Report
• The assessment in the AsA Quarterly Reports that the N70 value is at least
0.44 and 0.56 events per day appears to be an overestimate.
• The listing of mean Lmax aircraft noise levels for aircraft type includes data for
incorrectly attributed aircraft noise events and none of the mean Lmax aircraft
noise levels should be greater than 65dB(A).
Aircraft noise impact
• A major concern of the residents is sleep disturbance and there are no clear
criteria nationally or internationally.
• The guideline from Australian Standard 2021 [2000] for Lmax, inside the
bedroom not exceeding 50 dB(A) would correspond to an outside Lmax of
approximately 65 and 75 dB(A) for open and closed windows respectively.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
• The World Health Organisation [1999] guidelines for Lmax inside bedrooms of
45 dB(A) corresponds to an outside Lmax of 60 dB(A) assuming windows are
open.
• The World Health Organisation [2009] guidelines based on the health effects
of night time noise are given in terms of the noise level averaged over the
entire night.
The guideline and target levels for Lnight,outside assume open
windows and are 40 and 55 dB(A) respectively. The AsA data shows that
the current Lnight,outside at the NMT is around 42 dB(A). Modelling shows that
it would need over 500 aircraft during the night each with Lmax of 65 dB(A) to
increase the Lnight,outside to 55 dB(A).
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
1. INTRODUCTION
The extent of noise impact on the northern suburbs of Canberra from Canberra
Airport operations has been a source of complaint from some residents. These
residents are particularly concerned about the potential for increased aircraft noise
from future airport operations. In response to these concerns, Airservices Australia
installed a noise and flight path monitoring station in the suburb of Hackett for a
minimum period of 6 months to obtain quantitative data on the extent of the aircraft
noise impact for the region. The Acoustics and Vibration Unit of the University of
New South Wales at the Australian Defence Force Academy (UNSW@ADFA) was
appointed by the ACT Chief Minister’s Department to undertake an independent
assessment of information on aircraft noise from the data obtained with the following
main tasks:
• Consult with AsA Australia on the proposed monitoring arrangements
including the technical aspects of the study prior to the noise monitoring
terminal being commissioned;
• Observe AsA Australia’s establishment and commissioning of the noise
monitoring terminal at the selected site in Hackett;
• Undertake independent analysis of any interim data from the study made
available by AsA Australia including the correlation with flight path data; and
• Provide to the ACT Government a final report, which is suitable for public
release.
This report presents the findings by the Acoustics and Vibration Unit of the
assessment of the data provided by AsA Australia regarding the aircraft noise impact
in the suburb of Hackett in north Canberra. This report focuses on addressing the
tasks identified by ACT Chief Minister’s Department and broader issues on the
assessment of aircraft noise impact are outside the scope of the study.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
2. AIRCRAFT OPERATIONS AT CANBERRA AIRPORT
2.1. Aircraft Flight Paths
The operations that were of interest in this study were Regular Public Transport
(RPT) aircraft and General Aviation (GA) aircraft that overfly the vicinity of the
northern suburbs of Canberra. The main distinction between the two groups of
aircraft is that RPT aircraft, by routine, carry out a Standard Instrument Departure
(SID) and a Standard Terminal Arrival Route (STAR) under Instrument Flight Rules,
whereas the GA aircraft are generally flying under Visual Flight Rules (VFR).
The configuration of the two runways at Canberra Airport is shown in Figure 2.1.
RPT aircraft operations to the north of the airport involve departures using runway 35
and arrivals using runway 17. The noise levels generated by RPT aircraft arriving at
Canberra Airport and following a STAR are not as high as those produced by
departing aircraft, due primarily to the low engine power settings (approximately 50­
60% power) used by aircraft making an approach to land. Hence the focus for the
noise assessment for RPT aircraft operations in this assessment has been for those
carrying out a departure from runway 35.
GA aircraft can overfly the northern suburbs after take-off or while positioning to land
on either of Canberra airport’s two runways. Therefore, all operations of GA aircraft
overflying the northern suburbs have been considered in this assessment.
Figure 2.1: Runways used at Canberra Airport
and the directions referred to. [from
Airservices Australia, 2008]
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
2.1. Canberra Airport Noise Modelling
The method of assessing aircraft noise around an airport for planning purposes is
the Australian Aircraft Noise Exposure Forecast (ANEF) system. The system was
developed as a land use planning tool and the contours around the airport take into
account:
• the intensity, duration, tonal content and spectrum of audible frequencies of
the noise of aircraft take offs, approaches to landing, flyover and reverse
thrust after landing;
• the forecast frequency of aircraft types and movements on the various flight
paths, including flight paths used for circuit training; and
• the average daily distribution of aircraft arrivals and departures in both day­
time and night-time (day-time defined as between 07:00am and 07:00pm and
night-time defined as between 07:00pm and 07:00am).
An example of the ANEF contours for Ultimate Practical Capacity for Canberra
Airport in 2050 is shown in Figure 2.2 [from Canberra Airport 2009a]. This figure
shows the contours out to ANEF 25 are close to the flight paths and that the
residential area of North Canberra is well outside their extent. While ANEF contours
may be a useful planning tool, it is acknowledged that they do not give an indication
of the noise impact from aircraft operations throughout the day and various other
methods are used to better inform the community.
One is to show the noise level contour for each aircraft operation, i.e. a noise
footprint. Figure 2.3 and Figure 2.4 show the noise footprints for some common jet
RPT aircraft. The area of Hackett is outside the contour line showing the 65 dB(A)
impact region. The red box on these figures is the ‘high noise corridor’ which has
been identified by the airport with the goal that noisy aircraft operations are kept
within this corridor.
Noise footprints are useful in presenting information on the spread of noise from
individual aircraft operations but they do not provide information on the cumulative
effect of the number of aircraft movements. Another method for describing aircraft
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
noise is based on the number of events greater than a certain maximum noise level.
The number of events with maximum noise level greater than 70 dB(A) is referred to
as N70 and referred to in the AsA quarterly reports.
Figure 2.2: ANEF contours for Ultimate Practical Capacity for Canberra Airport in 2050 [from
Canberra Airport 2009a] The suburb of Hackett in North Canberra is indicated on this map.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 2.3: The predicted composite noise footprint from a 737-400 aircraft operating on
runway 35 or runway 17 at Canberra airport. Also shown but less clear is the predicted noise
impact for a DH8 aircraft arrival using runway 30 [from Canberra Airport 2009a ]. Hackett is
indicated by the circle on this figure.
Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 2.4: Predicted composite noise footprint from a 767-300 aircraft operating on runway 35
or runway 17 at Canberra airport. Also shown but less clear is the predicted noise impact for a
DH8 aircraft arrival using runway 30 [from Canberra Airport 2009a ]. Hackett is indicated by
the circle on this figure.
Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
2.2. Canberra Airport Noise Abatement Procedures
Canberra Airport does not currently have a timed curfew on aircraft operations.
There is a requirement that all aircraft comply with noise abatement procedures
defined in AsA Departures and Arrivals Procedures [Airservices Australia 2009e].
Applicable aircraft must remain clear of the noise abatement area which includes the
northern suburbs of Canberra, see Figure 2.5. This area extends vertically to 5000 ft
(1,524m) AMSL for propeller-driven aircraft with take-off weights greater than
5700kg which are generally turboprop-powered aircraft. The area extends to 7000 ft
(2,134m) AMSL for jet-powered aircraft. Most GA aircraft types are below the take­
off weight limit and so are not required to remain clear of the noise abatement areas.
Figure 2.5: Canberra
Airport noise abatement
area. [Airservices
Australia 2009e].
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
2.3. Additional Actions to Minimise Aircraft Noise Impact in North Canberra
Canberra Airport has implemented a number of measures in addition to the Noise
Abatement Procedures defined by AsA. In relation to operations over the inner
northern suburbs of Canberra these actions include the following [extracted from
Canberra Airport 2009b]:
• Revised departure procedures for Runway 30 - established 2001- see light
aircraft tracking straight over Fairbairn Avenue to the War Memorial before
turning off the original departure heading, thereby avoiding unnecessary noise
disturbance to residents of North Canberra, in particular the suburbs of
Campbell and Reid.
• Similar to the departure procedures for Runway 30, arriving aircraft on
Runway 12 are requested to join their final inbound track no later than the
War Memorial to reduce noise over North Canberra - established 2002. This
avoids aircraft turning late on to track over residential areas of Campbell and
Reid.
• New circuit procedures on the cross-runway (Runway 12/30) were
implemented to ensure minimum possible aircraft noise impact to residents in
Pialligo and North Canberra - established 2002
• Night (11pm-6am) operations - established 2003. Agreements were signed
with the two principal night freight operators at Canberra Airport to ensure
night freight aircraft use the main runway (Runway 17/35) rather than the
cross runway between 11pm and 6am, and fly clear of the Canberra and
Queanbeyan Noise Abatement Areas except where operationally required. A
similar agreement was reached with the Royal Flying Doctor Service/NSW Air
Ambulance and a further local aircraft operator. This ensures that residents of
Canberra and Queanbeyan, and particularly residents of North Canberra, are
subject to reduced over-flight at night.
It is interesting to compare the location of the noise abatement area and the high
aircraft noise corridor from the 2005 Master Plan for the Canberra Airport with the
locations on the 2009 Preliminary Draft Master Plan. There is a proposed extension
of the Noise Abatement Area to cover the newer suburban areas in Gungahlin. This
change needs to be considered in the context of safe operation of the airport and
would need to be agreed and prescribed by AsA Australia. Closer to the airport there
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
is little change to the ‘high noise corridor’ which is a noise control strategy
implemented by the airport.
Figure 2.6: Chart showing the noise
abatement area, hatched in green, and the
high noise corridor, with the red border, from
the 2005 Master plan for Canberra Airport.
[extracted from Canberra Airport 2005]
Figure 2.7: Chart showing the larger
proposed noise abatement area, hatched in
green and blue, and the high noise corridor
with the red border. From the 2009
Preliminary Draft Master Plan for Canberra
Airport. [extracted from Canberra Airport
2009c]
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
2.4. Standard Departure Procedures for Aircraft under Instrument Flight
Rules
It is usual for RPT aircraft and common for GA aircraft to operate under the
instrument flight rules (IFR) and hence follow a standard instrument departure (SID)
procedure which specifies the heading and altitude requirements that must be
followed after take-off. The departure plate for this procedure can be seen in Figure
2.8. For runway 35, the departure procedure specifies that aircraft make a slight
right hand turn after take-off. They then must climb to a minimum height of 3400ft
(1036m) AMSL (or 5000ft (1524m) AMSL when the air traffic control tower is not
active), before making a turn to a heading assigned by a radar controller.
Figure 2.8: “Canberra Six”
Standard Instrument Departure
plate for Canberra Airport.
[Airservices Australia 2009].
The procedures that are followed after this initial part of the departure track depend
on whether the aircraft is propeller or jet-powered and the general direction of its
destination. The departure plate for jet aircraft with destinations to the south and
west is shown in Figure 2.9. Aircraft with destinations to the west are required to
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
maintain a northerly heading until they have climbed to a height of 7000 ft (2,134m)
AMSL for jet aircraft or 5000 ft (1,524m) AMSL for propeller aircraft, before making a
turn to the left to take up their course. Assuming the ground level for much of the
suburban area is 600m above sea level, this ensures that jet aircraft should overfly
the noise abatement area at a minimum of 1500m above local ground level. In most
cases, the aircraft will be higher than 1500m above the ground level in the noise
abatement area as they continue climbing to a much higher cruising altitude.
Figure 2.9: Standard Instrument
Departure plate for Canberra
Airport for jet aircraft departing
to the south and west
[Airservices Australia 2009].
Examples of the actual tracks and altitudes of jet aircraft departing Canberra Airport
are shown in Figure 2.10 and Figure 2.11. These charts have been extracted from
recent quarterly reports issued by AsA Australia concerning the noise and flight path
monitoring carried out at Canberra Airport. Figure 2.10 shows all the jet departures
that occurred during a typical week (in this case the week from 2/12/08 to 8/12/08).
The colours of the track plots indicate the altitudes of the jet aircraft:
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Green
above 7000ft
Yellow
5000 to 7000ft
Orange
3000 to 5000ft
Red
2000 to 3000ft
These show that although jet aircraft do overfly some residential suburbs to the north
of Canberra on departure, during that month all the aircraft are abiding by the noise
abatement procedures and are above 7000ft. Figure 2.11 also shows that arriving jet
aircraft do not fly over the northern suburbs.
Figure 2.10: Jet aircraft departure tracks with altitude colour coded for a typical week, 2/12/08
to 8/12/08. [Reproduced from Airservices Australia 2008a].
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 2.11: Jet aircraft arrival tracks with altitude colour coded for a typical week, 2/12/08 to
8/12/08. [Reproduced from Airservices Australia 2008a].
2.5. GA aircraft procedures
The departure procedures that GA aircraft follow are not as strict as for RPT aircraft.
GA aircraft are generally light, propeller driven aircraft operating under Visual Flight
Rules (VFR) and fly at much slower speeds than RPT aircraft. Most have maximum
take-off weights less than 5,700kg and therefore are not required to comply with the
restrictions of the noise abatement area. Once a GA aircraft has completed a visual
takeoff and has climbed to a sufficient altitude, the aircraft is normally cleared to turn
and position on track to its destination. The procedure for an arriving aircraft is
similar, in that if the aircraft are above 3,500ft (1,067m) a controller will either instruct
the aircraft to fly specific headings or fly to prominent waypoints (e.g. Black
Mountain). If the aircraft is at an altitude of 3,500ft or lower, the pilot may track as
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Independent Assessment of A
Aircraft
ircraft Noise in Hackett, ACT 30 March 20
2010
10
they please while they are o
ou
utside
tside of the Canberra control zone but will be operating
under direction when they a
arre within the control zone. This zone can
can be seen in
Figure 2.12 and the inner co
con
control
ntrol
trol zone clearly encompasses the northern
northern suburbs of
Canberra. The cross runway (12/30) is used heavily by GA aircraft and
and while they
are in the control zone follo
follow
wing
ing instruction from a controller,
controller, the aircr
aircra
aft
ft do overfly
the northern and inner subu
subur
suburbs
rbs
bs of Canberra and this can be at altitud
altitu
altitudes
des
es less that
5,000ft (1,500m).
Figure 2.12: Map showing the control
zone for Canberra airport. [from
[from
Airservices Australia 200
2008]
8]
The great variation in the tra
tracks
trac
cks
ks and altitudes used by GA aircraft can b
be
e seen from
the tracks path charts for de
departing
parting GA aircraft in Figure 2.13 and for arriving GA
aircraft in Figure 2.14. It sh
sho
ould
uld be noted that,
that, due to the categorisat
categorisation
ion by AsA,
these plots are for all non-jet aircraft, not just non-RPT aircraft. Conseq
onsequently they
contain tracks flown by RPT p
propeller
ropeller-driven aircraft such as DH8, Metro
Metro 3 and J41,
which are subject to the nois
noise
e abatement procedures.
Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 2.13: Non-jet departures from Canberra Airport for a typical week, 2/12/08 to 8/12/08
[from Airservices Australia 2008a]. Note these plots are for all non-jet aircraft, not just GA
aircraft, and consequently contain tracks flown by RPT propeller-driven aircraft such as DH8,
Metro 3 and J41, which are subject to the noise abatement procedures.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 2.14: Non-jet arrivals from Canberra Airport for a typical week, 2/12/08 to 8/12/08 [from
Airservices Australia 2008a]. Note these plots are for all non-jet aircraft, not just GA aircraft,
and consequently contain tracks flown by RPT propeller-driven aircraft such as DH8, Metro 3
and J41, which are subject to the noise abatement procedures.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
2.6. Summary
Both RPT and GA aircraft operate at Canberra Airport. The standard operating
procedures, noise abatement procedures and additional measures implemented by
Canberra Airport aim to minimise overflights of residential areas.
Most RPT aircraft arrive from the south (runway 17) and depart to the north (runway
35). Noise abatement procedures define an area over which these RPT aircraft
cannot fly unless they are above 7,000 ft (2,134m) AMSL or approx 1,500m above
local ground level. The flight track data from AsA Australia shows that the majority of
jet aircraft comply with this noise abatement procedure. It is only on rare occasions,
usually when other safety factors apply, that there is non-compliance. Aircraft noise
modelling and the noise footprints for individual jet aircraft operations indicate that
noise levels over North Canberra should be less than 65 dB(A), which is the extent
of the noise footprint data.
GA aircraft can arrive or depart on either of the two runways but are always within air
traffic control while they are in the vicinity of the suburban areas of North Canberra.
Due to the orientation of the cross runway (12/30), which is used heavily by GA
aircraft, the aircraft can overfly the northern and inner suburbs of Canberra at
altitudes less that 5,000ft (1,500m) AMSL or approximately 900m above local ground
level. Measures have been implemented by the airport to minimise the noise impact
from GA aircraft by routing them over the non-residential areas as much as possible.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
3. CONCERNS OF RESIDENTS OF NORTH CANBERRA
Notwithstanding the AsA noise abatement procedures and additional measures
taken by Canberra Airport, there have been ongoing complaints about aircraft noise
from some residents in the northern suburbs of Canberra, primarily from the suburbs
of Hackett and Watson. Away from the main access roads, the general suburban
noise levels in these suburbs are low and especially along the eastern boundary (i.e.
closest to the airport) which is adjacent to that part of Canberra Nature Park
comprising Mt Ainslie and Mt Majura.
As part of the public consultation on the 2008 Preliminary Draft Master Plan for
Canberra Airport, many public submissions identified concerns about the current
noise impact and the potential for an increase of this impact from proposed
increases in aircraft operations.
In relation to noise issues, a common theme is that the maximum noise levels for
aircraft operations are already in excess of 65 dB(A) and this is particularly annoying
as the ambient noise level in the area is low. The residents expressed concern that
any expansion of the airport will further reduce their ability to enjoy the quiet amenity
in their gardens and intrude into their homes, especially during sleeping hours. Many
individual comments indicated great concern about the potential for increased night
time operations and the accompanying sleep disturbance this would produce. These
submissions sought the implementation of a formal night time curfew similar to that
which applies at Sydney Airport.
Curfew 4 Canberra is a community organisation with membership from the residents
associations of Pialligo, Hackett, Watson, North Canberra, Gungahlin and
Jerrabomberra. The organisation
has
the following core objectives
Curfew4Canberra, 2008]:
•
To secure an 11pm-6am curfew;
•
To oppose Canberra Airport becoming a 24 hour freight hub;
•
To oppose Canberra Airport becoming Sydney’s 2nd Airport;
•
To oppose the construction of a parallel (third) runway.
- 30 ­
[from
Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
As part of the campaign for a night curfew, the organisation quotes noise levels in
excess of “65dB(A) measured within North Canberra noise abatement areas for
B737 aircraft”. They also quote maximum noise levels of 67 dB(A) for jets, 72 dB(A)
for light aircraft and 74 dB(A) for helicopters. They consider that the assessment
and modelling procedures do not take into account factors such as temperature
effects on noise propagation and low background noise levels in the area. They
suggest that, in part, the higher than predicted noise levels are due to frequent
temperature inversions in the region.
3.1. Summary
There have been ongoing complaints about excessive aircraft noise from residents
in North Canberra and in particular from those in Hackett and Watson. These areas
are well away from main roads and adjacent to bushland. The main concerns are
that the maximum noise levels for aircraft operations are already in excess of
65 dB(A) and any expansion of the airport will further increase the aircraft noise
intrusion. The residents are particularly concerned about sleep disturbance from
night time operations and seek a formal night time curfew to be applied.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
4. MEASUREMENT AND ANALYSIS OF AIRCRAFT NOISE IN
HACKETT
4.1. Noise and Flight Path Monitoring
As part of its environmental responsibilities, AsA Australia has established a Noise
and Flight Path Monitoring System (NFPMS) at major airports around Australia. For
Canberra Airport, one permanent noise monitoring terminal (NMT) is installed to the
south of the airport in Jerrabomberra, directly under the flight path for runway 17/35.
In response to the concerns expressed about the high levels of aircraft noise in the
northern suburbs of Canberra, AsA undertook to install a portable Noise Monitoring
Terminal (NMT) in Hackett. The monitor was installed in late December 2008 at the
location indicated in Figure 4.1 and as shown in Figure 4.2.
The NMT consists of a microphone on a 6m mast and data acquisition facility and
transmitter. The noise level is continuously monitored and data transmitted to the
NFPMS central computer where it is processed and stored for later analysis. The
system is also linked with the secondary surveillance radar at the airport to acquire
flight track information on aircraft operating into and out of the airport. The operation
of the system is described as follows [Airservices Australia 2008c]:
When the level and duration of noise generated by any noise source in the
vicinity of the NMT location exceed the threshold level and duration that have
been set for the detection of aircraft noise, a noise event is recorded. The time at
which the noise event is recorded, and the NMT location where the noise event is
recorded, is checked against movement times and radar tracks of aircraft
operating in the vicinity. If the time and NMT location of the noise event match
the movement time and radar track of any aircraft, the noise event is attributed to
that aircraft. Otherwise it is regarded as part of the background noise.
The data stored by the NFPMS can be recalled to investigate details on particular
noise events or aircraft operations. The data is processed to provide the noise levels
in terms of various noise level descriptors. For assessment of the noise intrusion at
Hackett the relevant data is the maximum noise level, Lmax in dB(A), for the aircraft of
interest. The ‘A’ in this expression refers to a frequency filter which has a similar
frequency response to human hearing.
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Independent Assessment of A
Aircraft
ircraft Noise in Hackett, ACT 30 March 20
2010
10
Runway
Runway 35
departures
departu
res
Runway 30
departures
Figure 4.1: Screenshot from the Webtrak web application (discussed in Section 4
4.4)
.4) showing
the location of the noise monitor in relation to the airport and the suburb of Hacke
Hack
Hackett.
ett. [extracted
from Airservices Austra
Austr
Australia
alia 2009c with relevant departure directions add
ad
added]
ded]
ed]
Figure 4.2 Vie
View of noise monitor in location at Hackett
Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
4.2. Set up of the Monitor
A NMT is normally installed where overflying aircraft are the primary sources of high
noise events, such as the monitor to the south of the airport at Jerrabomberra.
Consequently the set up parameters, in particular the threshold level, are set to
minimise spurious data from general ambient noise events while capturing the higher
noise aircraft events.
For the installation in Hackett, direct overflight of the monitor by jet aircraft was rare
and many of the complaints refer to aircraft generally operating in the vicinity. It was
realised at the outset that even for GA aircraft that do overfly the area, the noise
from aircraft overflights could well be close to the noise level for other noise events
in the community.
Discussions were held with AsA regarding the optimisation of the set up parameters
to maximise the identification of aircraft noise events that could be close to the
ambient noise in the area while minimising the incorrect attribution of noise events to
aircraft. Following the initial set up, further adjustments were made and then the
system was left in place with the parameters as listed in Table 4.1.
The minimum rate of increase and decrease in noise levels were set by AsA at
0 dB/sec to capture the maximum number of noise events. This contributed to some
of the incorrect attributions of noise events to aircraft that are discussed later in this
report.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Table 4.1: Set up parameters for the NMT at Hackett.
Threshold, i.e. the trigger noise level above which the noise data is
considered potentially due to an aircraft.
Minimum rate of increase of the noise levels for the potential aircraft
noise event.
Maximum rate of increase of the noise levels for the potential aircraft
noise event. Rise times greater than this would be from events such as
explosives or similar sharp noises.
Minimum rate of decrease of the noise level after the maximum level
of the event has passed.
Maximum rate of decrease of the noise level after the maximum level
of the event has passed.
Pre-trigger measurement which allows for analysis of the data for
some time before the maximum level has been identified.
Post-trigger measurement which allows for analysis of the data for
some time after the maximum level has been identified.
55.0 dB(A)
0 dB/sec
5 dB/sec
0 dB/sec
5 dB/sec
5 sec
5 sec
4.3. Correlated noise events
An essential feature of the NFPMS data analysis is the capability to remove from the
data those noise events that are not related to aircraft i.e. by correlating noise events
with aircraft operations at that time. To achieve this, a “correlation circle” is identified
near the NMT. Once a noise event based on the parameters in Table 4.1 has been
identified, a check is made to see if there was an aircraft within the ‘correlation
circle’. If this check is positive, the noise event is tagged as being ‘correlated’ to that
aircraft. This noise event is then listed in a table giving the various noise descriptors
for the event along with the details for the aircraft considered responsible for the
noise event. The data for all the correlated or ‘tagged’ noise events are provided in
quarterly
reports
from
AsA
and
which
are
made
publically
available
(www.airservicesaustralia.com/projectsservices/reports/nfpms/nfpmscanberra.asp).
As well as providing information on the noise impact from the operations at the
airport this data can also be used to impose penalties on any aircraft operators that
did not comply with the applicable noise abatement procedures.
Most NMT are around major airports and the majority of aircraft flights are almost
directly over or close to the monitor. Thus a small correlation circle centred on the
monitor can be used to capture all the data that is required. For the installation in
- 35 ­
Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Hackett, it was clear from the outset that not all aircraft noise events would be from
aircraft flying close to the monitor so initially a correlation circle centred on the NMT
and with a radius of 2.5 km was chosen.
Following the analysis of the first month of data provided by AsA to the AVU, it was
clear that the location of the correlation circle did not allow for identification of any
noise events associated with jet aircraft operations that were following the tracks
specified by the SIDs and STARs. Following further discussions with AsA, it was
considered that the introduction of a second correlation circle might overcome this
problem (see Figure 4.3). The intention was that the processing of the data would
check if there was an aircraft in either circle and, if so, the noise event would be
considered to be correlated to that aircraft and would consequently be listed as such
in the quarterly report.
The investigation of the data of the first weeks of data on correlated aircraft noise
events provided by AsA showed that there could be both false positive correlations
and false negatives i.e. when there was an incorrect correlation to an aircraft or no
correlation to an aircraft when there should have been. To assist with the further
analysis of the data and to endeavour to ensure that any jet aircraft noise events
were correctly identified, AsA provided to the authors of this report (AVU) additional
data sets. One of these was the listing of all noise events at the NMT and another
was a listing of all jets flying through a ‘gate’ or cross sectional area across the flight
paths of the published SIDs.
The AVU analysed data for a typical week during the summer and outside holiday
periods (22/02/09-28/02/09) in an attempt to identify aircraft noise events by
matching the time that an aircraft passed through the ‘gate’ with the closest recorded
noise events. False correlations were removed by discarding any noise events that
occurred before the aircraft passed through the gate as the aircraft would be at such
a distance from the monitor that any noise event could not be related to the aircraft.
From consideration of the flight paths and the speeds it was assessed that any noise
event that occurred 30 seconds after the aircraft had passed through the ‘gate’
would not be from the aircraft because by that time the aircraft would be too far
away.
- 36 ­
Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
From the resulting listing of ‘manual’ correlations by the AVU it was found that the
data provided by AsA using two correlation circles did not include a number of noise
events that should be correlated with an aircraft. Further investigations led to the
implementation of a single correlation circle, large enough to capture the flight paths
of all aircraft departing the airport. The radius of this correlation circle was 4.25 km,
i.e. 8.5 km from one side to the other and the wide area covered can be seen in
Figure 4.4.
It is immediately apparent from Figure 4.4 that for a NMT at Hackett such a large
correlation circle would lead to incorrect aircraft ‘correlations’ with noise events at the
NMT. An aircraft only needs to be anywhere within that circle at the same time that
the noise level at the NMT meets the set up parameters for the event to be tagged
as a correlated noise event in the AsA data.
Essentially this means that the
maximum noise level for the majority of noise events at the NMT with a noise level
greater than 55 dB(A) would be considered to be the maximum noise level for an
aircraft that was somewhere in the large correlation circle. Careful analysis of the
data was therefore required in an attempt to identify those noise events which could
be correctly attributed to aircraft as opposed to those noise events that were falsely
attributed to aircraft.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 4.3: Two correlation circles used by AsA in the second analysis of the preliminary data
for the NMT at Hackett. It was expected that any noise event occurring at the NMT, indicated
by the blue square, for which an aircraft was found to be in either of the red correlation circles,
would be identified as resulting from that aircraft. However, this configuration of correlation
circles was found to lead to data errors and the configuration shown in Figure 4.4 was then
adopted by AsA for their analysis.
- 38 ­
Independent Assessment of A
Aircraft
ircraft Noise in Hackett, ACT 30 March 20
2010
10
Figure 4.4: The data from the NM
NMT
T presented in the AsA quarterly reports used th
the
e correlation
circle with radius 4.25 km. F
Fo
orr comparison, the smaller correlation circle for tthe
he NMT at
Jerrabomberra is also shown on
on this figure.
figure. [Extracted from Airservices Austra
Australia
lia 2009d].
Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
4.4. Webtrak
Around the time of the installation of the NMT in Hackett, AsA upgraded the
information on aircraft noise available to the public with a web based application
know
as
Webtrak
[www.airservicesaustralia.com.au/aviationenvironment/
noise/webtrak/default.asp]. This innovative application allows the public to view, for
all large airports around Australia, the flight paths and the noise level at any NMTs
near that airport. The interactive web page allows any user to view current data, with
a delay of 45 minutes included for security reasons. The historical data for aircraft
flight paths and ‘real-time’ readings from the noise monitors at that airport is
available for the previous 2 weeks.
Figure 4.5 is a screen shot from Webtrak showing aircraft flight paths for aircraft
operating at Canberra airport. The NMTs at Hackett and Jerrabomberra are
indicated on this screen shot as the small gray circles. Webtrak was also used by
the AVU during the analysis of the data from the NMT as it was particularly helpful to
indentify ‘false positives’. When there was an aircraft in the correlation circle and the
flight path on Webtrak showed that it was far away from Hackett, the noise level
indicated was more likely to be from a local event. Some examples of false positives
will be discussed in the next section of this report. At one stage during the project, it
was discovered that the two-week limit on the data had been removed and the
previous 3 months of data was visible. This proved to be extremely valuable in
viewing the flight tracks for some of the suspect correlated noise events. However,
the access to the historical data was then reinstated to only 2 weeks. This increased
the difficulty for the AVU to determine if correlated noise events were genuine
aircraft noise events as the track for each one being investigated had to be sought
from AsA.
- 40 ­
Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 4.5: Screenshot showing the Webtrak web application [extracted from
www.airservicesaustralia.com/aviationenvironment/noise/webtrak/info.asp]
4.5. Noise event details
From an analysis of the first data sets provided by AsA, it was clear that there were
both false positive and false negative correlations between aircraft in the area and
noise events. As there is no stored audio signal in the NFPMS, the only way to
further investigate these was to view a profile of the noise level versus time for each
event and attempt to judge if the profile was typical for an aircraft noise event. The
flight track was also helpful in this analysis. This level of detail for each noise event
is available within the NFPMS. However as seeking such detail took some time and
required AsA staff to individually extract the profile and the flight track, selected
noise events were identified by the AVU as warranting further investigation. AsA
then provided the noise level versus time profiles and flight tracks for each of those
events.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
The analysis of the detailed data showed several areas where the setup of the noise
monitor and the correlating methods provided inconclusive or incorrect attributions of
aircraft noise events. These shortcomings of the basic data sets are discussed in the
following sections.
As long as an event satisfied the parameter settings, the NMT recorded a noise
event. Thus noises which are part of the residential/nature park area, such as birds,
a loud vehicle, construction noise, rain falling around the noise monitor etc could be
noted as noise events. Figure 4.6 is an example of such an event with a noise level
of 55 dB(A) although there is no aircraft in the area. AsA did provide the AVU with a
complete listing of all the noise events that were recorded over a period within the
2009 first quarter and this data was used to compare the levels for correlated aircraft
noise events with levels for all noise events that met the parameter settings.
Figure 4.6: Screenshot from the Webtrak system showing an instance where a noise event has
been identified when there were no aircraft in the vicinity.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Obvious false positive
A false positive ‘correlated’ noise event can occur when the noise event is identified
i.e. the NMT parameter settings are satisfied, and there is an aircraft somewhere in
the correlation circle. Inspection of the time profile and/or checking the flight path can
assist to identify if that noise event is due to that aircraft.
An example of a false positive correlation is a noise event with an Lmax of 64 dB(A)
which was attributed to a Mooney M-20P aircraft (see Figure 4.7). However, the
noise profile (Figure 4.8) is not characteristic of an aircraft at all. The likely cause of
the consistent high noise level shown in the profile is rain striking a surface near the
NMT. A check of the Bureau of Metrology data shows that indeed there was high
rainfall on this day. A similar occurrence in the second quarter is shown in Figure
4.8 where the Lmax of 78.7 dB(A) has been attributed to a DH8 aircraft departing
when there were heavy rain storm in the area.
Another example of a falsely correlated event is shown in Figure 4.10. This noise
event was identified with the flight of a Cessna 150 aircraft that was within the
correlation area at the time. The noise profile shows the time of the event is very
short for such an aircraft flyover and the level barely gets above 55 dB(A) on two
occasions.
Fully accounting for single noise events that are incorrectly attributed to aircraft in
the AsA data would require viewing of all the noise event profiles individually which
would be an impractical, time consuming task.
- 43 ­
Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 4.7: Image of the M-20P
aircraft that was within the correlation
circle and which was attributed as the
cause of the noise event [reproduced
with approval from © L. Brendan,
from Airliners.net]
Figure 4.8: Noise level versus time for the noise event that was incorrectly attributed to a M­
20P aircraft [provided by Airservices Australia].
- 44 ­
Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 4.9: Noise level versus time for the noise event that was incorrectly attributed to a DH8
aircraft and more likely to have resulted from rainstorms in the area [provided by Airservices
Australia].
Figure 4.10: Noise profile for a noise event on 02/01/09 at 14:27with Lmax of 55.3 dB(A) and
attributed to a Cessna 150 aircraft [provided by Airservices Australia].
- 45 ­
Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Multiple correlated noise events for only one aircraft operation
The NMT data also included attribution of more than one correlated noise event to
one aircraft operation. Figure 4.11, shows a sequence of screenshots from Webtrak
for a light aircraft approaching the noise monitor and flying almost directly overhead.
When the aircraft was approaching, but at some distance from the noise monitor, an
event was recorded with a level of 65 dB(A). As the aircraft was within the correlation
circle this noise event was attributed to that aircraft. However, it is uncharacteristic of
aircraft noise that at such a distance from the NMT, this could be a true indication of
the noise level from such an aircraft.
After this first apparently correlated noise event, the level at the NMT dropped to
below the trigger level of 55 dB(A). If the first event was truly from the aircraft the
level would be expect to gradually increase and not drop by over 10 dB. The second
image shows that when the aircraft was much closer to the monitor another
correlated event is recorded with a level of 56 dB(A). It is reasonable that this noise
event is correctly attributed to the aircraft.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 4.11: Webtrak screenshots showing a sequence with a falsely correlated noise event.
The left shot shows the aircraft at some distance from the NMT at the same time as there is a
noise event level of 65 dB(A). The right shot shows the aircraft close to the monitor and a
noise event level of 56 dB(A).
Another example of this is the multiple noise events due to a C150 aircraft recorded
on the 22/01/09. The first correlated noise event for this aircraft began at 08:16:32
with the noise profile in Figure 4.13. The second noise event began at 08:17:43 with
the profile in Figure 4.14. From the shape and short duration, the first profile is
considered more likely to result from local community noise and only because the
aircraft was somewhere in the correlation circle was this noise event attributed to
that aircraft. The second profile and time duration is more characteristic of that which
would be expected from an aircraft overflying the NMT and the Lmax for this event
was 66.5 dB(A).
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 4.12: Image of the Cessna 150 (C150) type aircraft that was within the correlation circle
and which was attributed as the cause of the two separate noise events [reproduced with
approval from © J. Adams, from Airliners.net]
Figure 4.13: Noise level versus time for the first noise event at 08:16:34 that was attributed to
the C150 aircraft with a Lmax of 59 dB(A) [provided by Airservices Australia]. It is considered
that this noise event is from a local noise and not the C150 aircraft.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 4.14: Noise level versus time for the second noise event at 08:17:14 that was attributed
to the same C150 aircraft with a Lmax of 67 dB(A) [provided by Airservices Australia]. It is
considered that this noise event could be correctly attributed to the C150 aircraft.
The occurrence of multiple noise events attributed to the same aircraft was found to
occur more frequently for non-jet GA aircraft such as C150, C172 etc which operate
at slow speed. That means they remain within the correlation circle for some time
thus increasing the risk that local noise events could occur during this period and be
incorrectly attributed to the aircraft. However, with the large correlation circle that
was required to capture the flight paths of RPT aircraft, some instances of multiple
noise events were also found for RPT aircraft.
Further analysis was needed to remove as many of these incorrectly attributed noise
events as possible. The data was examined for multiple correlated noise events for
the same aircraft that were only separated by a short time. In each case, it was
assumed that only one of the events should be attributed to the aircraft while the
other events were false attributions. The most likely genuine event was assessed
from examination of as much collaborative data as possible such as duration of the
event, time between events, knowledge of aircraft type operations etc. Access to the
Webtrak historical data over the period would have been of some assistance in this
analysis but such data is only available for the current two-week period. The only
reliable way to remove the false data would be to view the noise profile or listen to
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
an audio recording of every noise event. Such detailed analysis was not practical for
this project and an audio playback for noise events is not available.
Correctly attributed noise event with incorrect maximum noise level
The Lmax is the maximum noise level that occurs during the time of the noise event
and it is possible that the maximum noise level could result from a local noise event
that was higher than the noise from a nearby aircraft. For the usual placement of the
NMT near to the flight path, where both the number of aircraft flyovers and aircraft
noise levels are high, the occasional occurrence of an incorrect noise level has only
a small effect on the statistical data. For the placement at Hackett, the total number
of aircraft operations is less than for a major airport and many community noise
events were of similar or greater level than the aircraft noise events. Consequently,
an incorrect maximum noise level for correctly attributed aircraft noise levels is more
likely.
Figure 4.15 shows one such example – in this case for a Boeing 737-400 aircraft.
The shape of the profile with multiple peaks as high as 80 dB(A) does not match the
typical flyover or passby noise level for an aircraft and the noise event is most likely
to result from local noise sources. The underlying profile with a maximum noise level
around 65 dB(A) is more likely to be the true noise level for this aircraft noise event.
Another example of an incorrect maximum noise level is shown in Figure 4.16, in this
case for a GA aircraft, a Cessna 172. This noise profile shows a sharp maximum to
86 dB(A) with a consistent underlying noise around 65 dB(A). The maximum noise of
86 dB(A) followed by the sharp drop from 86 dB(A) to 60 dB(A) in a one second
interval is uncharacteristic of the noise from a Cessna 172.
The quarterly report on the NFPMS Canberra for the period January to March 2009
[Airservices Australia 2009d] identified multiple peaks in a noise profile as an
indication of incorrect noise level for an aircraft. The quarterly report states [p12]
that checks were made on 140 correlated noise events with Lmax greater than
70 dB(A) and:
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
… 72% of these were events with multiple peaks in the noise recording
which are typical of community noise events. Note an aircraft noise event
will have a single peak. Given this, the N70 value for the Hackett monitor
presented in Table 1 should be considered an over-estimate…
The AVU attempted to further investigate this by checking with published data for
aircraft types [from Federal Aviation Administration, 2002] as well as checking the
time duration for the noise event and the comparison between the various noise
descriptors that are included in the AsA data set. For selected events, the noise level
profile was sought from AsA to assist with this assessment. However, even after this
analysis it is likely that the findings presented in this report still includes some noise
levels attributed to aircraft that are higher than the actual aircraft noise level. Again,
the only reliable way to fully correct the data would be to view the noise profile or
listen to an audio recording of every correlated noise event but such detailed
analysis was not practical for this project.
Figure 4.15: Noise profile for a correlated noise event. In this case, the noise event was
correlated with a Boeing 737-400 aircraft operated by Qantas Airways and included in the AsA
data as having Lmax of 80 dB(A)..
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 4.16: Noise profile of the noise event correlated with a Cessna 172 aircraft and included
in the AsA data as having Lmax of 86 dB(A).
4.6. Non aircraft noise levels
As discussed above and in later sections of this report, the NMT at Hackett is subject
to a variety of local noises than can lead to errors in the data when the local noise is
in excess of the noise from the aircraft somewhere in the correlation circle. The
sources of noise that are typical for such a residential area on the boundary of a
nature park include birds, cars, gardening equipment etc as well as natural sounds
from thunder, high winds and rain. To obtain an indication of some of these noise
levels, attended monitoring was undertaken during 1600 to 1700 hrs on 19/10/2009
and 0630 to 0730hrs on 20/10/2009. A Bruel and Kjaer sound level meter type 2250
was set up on a tripod near to the NMT location. The meter was calibrated before
and after the measurements.
The data in terms of LAeq over 1 second and an
identification of the source of the noise was stored for later analysis.
This is
essentially the same descriptor for noise that is presented on the noise level versus
time profiles from the NFPMS.
Many local sounds were found to have noise levels in the range 55 to 60 dB(A)
which would be sufficient to be identified as noise events by the NFPMS. Higher
noise levels were found for some bird songs as shown in Figure 4.17. The birds
were the dominant source of noise during this 10 minute period and noise levels
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
close to 65 dB(A) were measured at the ground level location. At the elevated
height of the NMT these noise levels could be considerably higher as the birds could
be much closer to the microphone.
The sounds during the measurements on
19/10/09 were from general bird life in the area, predominantly magpies and
currawongs. None of the more raucous birds such as galahs and white cockatoos,
which could produce considerably higher noise levels, were singing at that time.
Also note on this chart that the sound from the birds can be prolonged high noise
levels as in the first portion of this figure or short spikes as in the second part.
Figure 4.17: Sound pressure level, dB(A), versus time for attended noise monitoring during the
morning of 20/20/2009.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
4.7. Summary
Within the NFPMS, the attribution of a noise event to an aircraft is based on an
aircraft being within the correlation circle at the time the noise event satisfies the
criteria set for that NMT. Most installations are near a flight path where the aircraft
noise is likely to be the dominant noise in the area. For the installation at Hackett,
the aircraft noise levels are close to the local environmental noise levels and there is
greater chance of local noise events, such as cars, gardening equipment and birds
etc, being incorrectly attributed to aircraft. The initial analysis identified some clearly
incorrectly attributed noise events and techniques were developed to remove such
events from further analysis. However, the remaining data sets may well still include
such false positives. One way to correct the data would be to view the noise profile
and/or listen to an audio recording of every noise event but such detailed analysis
was not practical for this project.
The initial analysis of the data identified that there were false negatives, i.e. noise
events that were noted by observers as due to RPT aircraft but were not attributed to
RPT aircraft in the data set.
Various attempts to improve the correlation were
attempted by AsA and eventually a single large correlation circle was implemented.
While this very large correlation circle overcame the problem of missed aircraft
events it increased the incidence of incorrectly attributed noise events, i.e. ‘false
positives’. Techniques were developed to further remove these but the data sets
may well still include some false positives.
Another problem with the data set was the occurrence of multiple correlated noise
events for the one aircraft, particularly for slower moving GA aircraft. Only one of
these events should be attributed to the aircraft. The data was examined manually
to remove multiple events using as much collaborative information as possible. A
further error in the data is the incorrect attribution of noise level for a locally
generated noise to an aircraft which was somewhere in the large correlation circle at
the same time. This local noise can appear as one or more peaks in the noise profile
superimposed on the shape of a typical noise profile for a passing aircraft.
Techniques were developed to attempt to remove these but the data sets may well
still include some incorrect noise levels for correctly attributed aircraft noise events.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
5. NOISE LEVELS FOR REGULAR PUBLIC TRANSPORT AIRCRAFT
5.1. General
This section discusses the correlated results from the NMT due to Regular Public
Transport (RPT) aircraft.
For the analysis, all aircraft that were turbo-prop or jet powered aircraft were
categorised as RPT aircraft. The justification for this was that nearly all of these
aircraft types are above the minimum weight required by the noise abatement
procedures. By making this distinction, aircraft such as military turboprop and jet
types (e.g. C130, BAE Hawk) and smaller turboprop types operated by charter
companies (e.g. Cessna 441) were included as RPT aircraft although they may not
have been carrying out scheduled RPT operations. The AsA data processed using
the single large correlation circle shown in Figure 4.4 were used for this assessment
of RPT aircraft noise levels.
The bulk of the analysis has been made on the AsA data for the first quarter of the
installation, i.e. over the period Jan to March 2009. The AsA report for the second
quarter, i.e. over the period April to June 2009, was released in October and showed
similar distribution of noise levels for RPT aircraft. Techniques developed during the
analysis of the first quarter data were used to review this data and selected samples
of the higher correlated noise events were identified for further investigation.
During the period from 18/12/08 to 28/04/09, the Hackett NMT data reported 3,200
events identified as correlated with an RTP aircraft and a similar number were
identified during the second quarter. However, as discussed in the previous section
of this report, some of these RPT correlated events were not valid. In particular the
data included many multiple events (i.e. two or more consecutive noise events)
supposedly correlated with a single aircraft. As the RPT aircraft were following a
flight path and so only passing thought the area once, these multiple events could
not all be valid aircraft noise levels.
They were more likely local events that
happened to be above the threshold during the time that the RPT aircraft was
somewhere inside the large correlation circle. The first step to clean up the first
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
quarter data was to remove these multiple events keeping only those with the higher
value of Lmax, or for which the time duration of the event was similar to that for a valid
aircraft noise event. The original 3,200 potentially aircraft noise events over the 132
days were thus reduced to 2,714 noise events, i.e. almost 21 per day.
The only way to determine if each of these potential 2,714 RPT aircraft noise events
resulted from community noise or aircraft noise would be to examine in detail the
noise profile for each event and the track path for the RPT aircraft with which it was
correlated. The techniques discussed in the Section 4 of this report were applied to
remove as many incorrectly attributed RPT aircraft noise events as possible.
Although the remaining data may still include noise events incorrectly attributed to
RPT aircraft it does provide a fair indication of the noise impact from RPT aircraft.
For the majority of these potential RPT aircraft events, the Lmax levels were between
55dB(A) and 65dB(A).
5.2. Frequency of RPT aircraft noise events
Figure 5.1 shows the distribution of the noise events attributed to RPT aircraft
according to the hour of the day during which they occurred. The shaded part of
each bar represents the total number of noise events in the original data correlated
with RPT aircraft and the solid part the remaining events after the multiple events
had been filtered out, as discussed in section 5.1. This figure shows the higher
number of correlated RPT aircraft noise events between 0600 and 1000 and
between 1700 and 1900 which corresponds with the busiest period of operations at
the airport.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 5.1: Distribution of noise events over the period from 18/12/08 to 28/04/09 and attributed
to RPT aircraft according to the hour of the day during which they occurred.
Figure 5.2 shows the distribution of correlated noise events according to the day of
the week on which they occurred. It can be seen that the frequency of RPT aircraft
events near the NMT is consistent across weekdays with a reduction in the number
of events on the weekend which corresponds to a lower number of scheduled flights.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 5.2: Distribution of noise events attributed to RPT aircraft, over the period from 18/12/08
to 28/04/09, according to the day of the week on which they occurred.
Figure 5.3 shows the distribution of the correlated noise events during the first
quarter according to the type of RPT aircraft operation. The majority of the recorded
events were correlated with aircraft departing the airport to the north using runway
35. A small proportion of the apparently correlated with noise events included aircraft
that were arriving from the north and landing on the same runway toward the south.
Arriving aircraft were not expected to generate sufficient noise to trigger the NMT
due to the reduced engine power settings used while carrying out an approach. In
addition, local residents had not identified approaching aircraft to be a concern. This
further indicates that the data still included community noise events that had been
incorrectly attributed as being due to an RPT aircraft that was somewhere in the
large correlation circle.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 5.3: Distribution of noise events attributed to RPT aircraft, over the period from 18/12/08
to 28/04/09, according to the type of operation being carried out.
5.3. Worst-case RPT aircraft noise events
From the first data set provided by AsA, covering the period 18/12/08 to 28/02/09
using the small correlation circle, 18 noise events were correlated with RPT aircraft.
This was surprising as RPT aircraft following standard fight paths and complying with
noise abatement procedures would not be expected to be within the small correlation
circle that applied for that data set. It was discovered that these RPT aircraft had not
followed the standard flight paths and had flown very close to the NMT. This data
was useful because the closeness of the aircraft flight paths to the noise monitor
gave an indication of the worst-case noise levels that could be expected from RPT
aircraft. The timing and flight paths indicated that the reason for the violation in 10
instances was weather related. Strong storm cells in the area, i.e. hazardous
weather, can justify non-compliance with the noise abatement procedures and
aircraft will be directed along flight tracks within the noise abatement area.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
One particular instance of this was the evening of the 23/02/09 when between
4:45pm and 5:15pm there were three noise events correlated with RPT aircraft. The
details for the noise events are shown in Table 5.1 and flight paths in Figure 5.4. It is
relevant to note that the aircraft identified as #4 flew close to the NMT but did not
generate a correlated noise event.
The historical meteorological data for those times showed that large storm cells were
to the north of Canberra. Permission would have been sought to avoid these storm
cells on the basis of safety. As these RPT aircraft flew either directly over or close to
the NMT at low altitudes, these noise events with Lmax of 75.6dB(A), 65.7dB(A) and
76.4dB(A) respectively can be considered to be the ‘worst case’ noise levels for jet
RPT aircraft in North Canberra. Any apparently correlated noise events for RPT
aircraft complying with noise abatement procedures should be considerably less
than for these three flight tracks. The noise profile for event identified as #1 is shown
in Figure 5.5. This profile is typical of a jet-powered aircraft flying directly overhead a
NMT at low altitude. It should be noted that the noise event is quite long in duration,
approximately 40 seconds and the rate of rise and fall of the noise level are nearly
equal.
Table 5.1: Details for aircraft that flew outside the noise abatement area on the evening of
23/03/09 [extracted from data set provided by AsA].
Ident
number
#1
#2
#3
#4
Event
Time for LAmax
LAmax
date
23/02/09
16:49:10
75.6
23/02/09
17:11:05
65.7
23/02/09
17:13:38
76.4
This aircraft did not generate a noise
event
- 60 ­
Aircraft
type
E190
E170
B734
B737
Operation
D
D
D
D
Runway
used
35
35
35
35
Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 5.4: Flight paths for RPT aircraft that
flew outside the noise abatement area during
the evening of 23/02/09 [provided by AsA].
The noise monitor terminal location is
designated with the small box.
Figure 5.5: Noise profile for E-190 aircraft (indicated as #1 in Table 5.1) that flew directly
overhead the noise monitor terminal. Note the generally steady rise and decrease in noise
level on either side of the higher noise levels when the RPT aircraft was close to the NMT.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Another ‘worst case’ event was the direct overflight of Hackett by an F-18 military
aircraft which occurred on the evening of the 25/01/09 (the day before Australia
Day). The track of the aircraft is shown in Figure 5.6. The first noise event was
identified when the F-18 aircraft was travelling toward the southwest. The jet was
travelling at a speed of 280 knots (518 km/hr) and at an altitude of approximately
3,350ft AMSL (approximately 400m above ground level). The noise profile is shown
in Figure 5.7. The Lmax was 81.9 dB(A) and the event only lasted 28 seconds due to
the high speed of the aircraft.
The profile for the second noise event is shown in Figure 5.8. In this instance, the
aircraft passed to the south of the NMT and was climbing rapidly at the time. The
Lmax for this second noise event was 89.8 dB(A), considerably higher than the Lmax
for the first event. The second event was also longer, lasting 120 seconds.
The 8 dB difference in noise levels relates to the difference in the operation of the
jet. In the first instance, the aircraft was cruising and using a low engine power
setting whereas the second event occurred while the aircraft was climbing and
accelerating with high engine power settings and possibly with the aircraft’s
afterburner being used.
Figure 5.6: Track of an F-18 military jet that directly overflew Hackett while tracking southwest
before generating a second noise event while climbing to the northeast on departure from the
Canberra airspace.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 5.7: Noise level versus time profile associated with the direct overflight of Hackett by
an F-18 military jet.
Figure 5.8: Second noise level versus time profile associated with the overflight of the F-18
military aircraft.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
5.4. Noise levels for RPT aircraft events on specific days
As described in Section 4 of this report, even after filtering out the multiple noise
events it was clear that the data still contained incorrectly attributed aircraft noise
events. As it was impractical to fully investigate every correlated noise event over the
period sample days were selected for detailed analysis. Two weekdays and a
weekend day outside holiday periods were selected. Friday 27/02/09 was selected
as a typical busy weekday and Wednesday 07/01/09 was chosen because it was
found to have six noise events above 65dB(A) apparently correlated with aircraft.
Saturday 03/01/09 was a typical weekend day and was chosen because data had
been provided by a local resident of aircraft sightings for this day, providing a second
source of verification for the correlated noise events. From the second quarter data
Wednesday 22/07/09 was chosen as it had a high number of correlated RPT aircraft
and observational data was available from a Hackett resident.
5.4.1.
Typical Weekday in First Quarter
Figure 5.9 shows the noise levels for the 36 potential RPT aircraft noise events for
Friday 27/02/09. The majority of correlated noise events have Lmax between 55 and
65 dB(A) and only one noise event is above 65 dB(A). For comparison, Figure 5.10
presents all of the noise events recorded by the NMT on the same day. This shows
that there were 19 noise events not attributed to aircraft activities that had Lmax
values above 65 dB(A) with the loudest being 76.3 dB(A).
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 5.9: Noise levels of potential RPT aircraft noise events for Friday 27/02/09.
Figure 5.10: Noise levels for all noise events for Friday 27/02/09. The events potentially
correlated with an RPT aircraft are labelled with black solid squares.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
5.4.2.
Noisy Weekday in First Quarter
Figure 5.11 shows the noise events that were correlated with aircraft for Wednesday
07/01/09. This day was selected as it contained an unusually high number of aircraft
noise events above 65 dB(A) and warranted further investigation. For this day there
were two noise events above 70 dB(A) and a further three above 65 dB(A).
Figure 5.11: Noise levels of potential RPT aircraft noise events for Wednesday 07/01/09. The
labelled events are discussed below.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 5.12: Noise levels for all noise events for Wednesday 07/01/09. The events potentially
correlated with an RPT aircraft are labelled with black solid squares.
Figure 5.12 shows all of the recorded noise events for Wednesday 07/01/09 with the
aircraft noise events marked with black squares. It can be seen that the correlated
aircraft noise events with maximum levels higher than 65 dB(A) occurred during
periods when there were a number of other uncorrelated noise events between 65
and 80 dB(A). The validity of the high aircraft noise levels was investigated by
looking at the noise profiles and the aircraft tracks. The profiles for these four events
are discussed below. The detail indicates that the noise levels attributed to these
four aircraft are most likely incorrect. Without going through all correlated noise
events one by one in this manner it is impossible to determine the extent of such
false attribution.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Event 1
Figure 5.13 shows the noise profile for the loudest correlated noise event,
71.2 dB(A), which was attributed to a Qantas 737 aircraft. By comparing the noise
profile for this event with the noise profile for events that are known to be for aircraft
(eg as shown in Figure 5.5) it can be seen that this noise event is uncharacteristic for
an aircraft as the duration of this noise event (<10 seconds) is too short. Also, by
comparing the noise profile with those for the RPT aircraft that flew right over the
NMT, and viewing the flight path which is quite a distance from the NMT, it is
uncharacteristic that this aircraft generated a noise level greater than 70 dB(A) at the
NMT.
Figure 5.13: Noise profile (left) and flight path (right) for a noise event that was attributed to a
Qantas 737 aircraft.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Event 2
In a similar manner, the noise profile for the second loudest noise event that
occurred on Wednesday 07/01/09 is shown in Figure 5.14. The Lmax for this noise
event was 70.9 dB(A) and was attributed to a 737 aircraft operated by the Royal
Australian Air Force (RAAF). Again, the duration of the noise event is less that 20
seconds and the sharp drop in the noise level from above 70 dB(A) to less than
65 dB(A) is not characteristic of an aircraft noise profile. If these two spikes are
removed from the profile, there is a remaining shape that does match that typical for
an aircraft with an Lmax around 63 dB(A).
Figure 5.14: Noise profile (left) and flight path (right) for a noise event that was attributed to a
RAAF 737 aircraft. The Lmax of 70.9 dB(A) appears to be an incorrect attribution due to a local
noise and the maximum level is more likely to be 63 dB(A)
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Independent Assessment of A
Aircraft
ircraft Noise in Hackett, ACT 30 March 20
2010
10
Event 3
Figure 5.15 shows the noise profile and flight path for a third correlated noise event
68.7 dB(A). It
from Wednesday 07/01/09, attributed to a DH-8 aircraft with Lmax of 68
can be seen in this profile th
tthat
hat
at there is an underlying noise of long dur
duration
duration
ation that is
between 55 and 60 dB(A) th
that
tha
att could be caused by an aircraft, however the peak at
the beginning of the noise ev
e
event
vent
ent is too short in duration to be caused by
by an aircraft.
Checking the flight path the aircraft
aircraft took, it can be seen that the aircraft make a turn
to the right to ‘dog leg’ its tr
tra
ack
ck taking it well away from the area wher
where the noise
monitor is located.
Figure 5.15: Noise profile (left)) ffor
or a noise event that appears to be incorrectly at
attributed to a
a
Qantas DH-8 air
aircraft
craft with the flight path shown on the right.
Figure 5.16: Image of a DH-8 air
airc
craft which is aircraft type to which the noise eve
event
nt in Figure
5.15 was attributed [reprodu
[reproduced with approval from © J. Gilbert, from Airline
Airliners.net
rs.net].
Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Event 4
Figure 5.17shows the noise profile and flight path for the fourth correlated noise
event from Wednesday 07/01/09. The aircraft in this instance was an Embraer E-170
operated by Virgin Blue. The Lmax in this instance was 69.9 dB(A). Not only is the
time period for the event shorter than would be expected for an aircraft noise event,
the sudden drop in noise level of over 10 dB within the event is not typical for the
profile for an aircraft. The maximum level appears to be incorrectly attributed to this
aircraft departure.
Figure 5.17: Noise profile (left) and flight path (right) for a noise event that was attributed to a
Virgin Blue E-190 aircraft.
5.4.3.
Typical Weekend day in First Quarter
Figure 5.18 shows 15 potential RPT aircraft noise events for Saturday 03/01/2009.
For comparison, Figure 5.19 shows all of the noise events recorded by the NMT on
the same day. Again, there were many noise events not correlated with aircraft and
that were within and above the same noise level range.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 5.18: Noise levels of potential RPT aircraft for a typical weekend day, Saturday 03/01/09.
The noise profiles for the labelled points are shown in Figure 5.20.
Figure 5.19: Noise levels for all noise events for Saturday 03/01/09. The events potentially
correlated with an RPT aircraft are labelled with black solid squares.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
This Saturday was of particular interest as there were observations of noise levels
and aircraft sightings by a Hackett resident and this data was compared with the
correlated noise level data. Noise profiles were requested from AsA for three of the
correlated noise events that agreed with the observations of the resident; one in the
early morning, one near the middle of the day and one from the evening. These are
identified as 1, 2 and 3 on Figure 5.18 and three profiles are shown in Figure 5.20
with the data given in Table 5.2.
The profiles for events 1 and 2 are similar in that they both show a rise in sound level
from a background noise level of approximately 45 dB(A) to approximately 60 dB(A).
Apart from slight fluctuations, the sound level remains high for approximately 30
seconds before gradually dropping back below the threshold of the noise monitor
terminal. The profile of the third event, although correlated with an aircraft within the
area shows a different profile. The independent observer did record noise from an
aircraft at a time of 19:08 with a sound level of 56 dB(A) i.e. just above the 55 dB(A)
threshold for the NMT. So there was clearly an RPT aircraft visible from Hackett with
a noise level just around the threshold for the NMT. The noise event that has been
correlated with this RPT aircraft is at 19:09 with an Lmax of 61 dB(A). It is therefore
more likely that this apparently correlated RPT aircraft event as recorded in the NMT
data with an Lmax of 61 dB(A) is due to a local community noise and not to an RPT
aircraft. This highlights that the data set still includes incorrectly attributed noise
levels when an RPT aircraft is somewhere in the correlation area.
Table 5.2: Details of the noise events shown in Figure 5.18 and the profiles shown in Figure
5.20.
Event number
Time
Duration
Lmax dB(A)
1
06:44:25
29 sec
60.6
2
10:28:12
28 sec
58.8
3
19:09:22
9 sec
61.3
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
1
2
3
Figure 5.20: Noise profiles for 3 selected noise events that occurred on Saturday 03/01/09. The
details for the noise events are listed in Table 5.2.
Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
5.4.4.
Busy Weekday in Second Quarter
Figure 5.21 shows all the correlated aircraft noise events for Wednesday
22/07/2009. There were a high number of correlated aircraft noise events for this day
and observational data was provided by a Hackett resident. The noise profiles and
flight paths for the six of the correlated RPT aircraft for this day were obtained from
AsA and are discussed below.
#4
#3
#2
#5
#6
#1
Figure 5.21: Lmax versus time of day for all the apparently correlated noise events on
22/07/2009.
Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Event 1
Figure 5.22 shows the noise profile and flight path for the correlated noise event
identified as #1 on Figure 5.21. The aircraft in this instance was an Embraer E-190
operated by Virgin Blue. The Lmax for this correlated noise event was 63.1 dB(A).
The profile shows a number of spikes which would be more likely representative of
local noises and not due to the aircraft.
Figure 5.22: Noise profile (left) and flight path (right) for a noise event that was attributed to a
Virgin Blue E-190 aircraft.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Event 2
Figure 5.23 shows the noise profile and flight path for the correlated noise event
identified as #2 on Figure 5.21. The aircraft in this instance was a B737-800 aircraft
operated by Qantas. The Lmax for this correlated noise event was 65.6, dB(A). The
profile does show an uneven pattern but the time for the event is typical for a valid
aircraft event. There may have been some local noises that have lead to some of
the spikes on this profile but it is reasonable that the Lmax for the aircraft could be
near 65 dB(A).
Figure 5.23: Noise profile (left) and flight path (right) for a noise event that was attributed to a
B737-800 aircraft operated by Qantas.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Event 3
Figure 5.24 shows the noise profile and flight path for the correlated noise event
identified as #3 on Figure 5.21. The aircraft in this instance was a Virgin Blue E-190
aircraft. The Lmax for this correlated noise event was 66.6, dB(A). The profile for this
event is too short for the maximum noise level to be due to an aircraft. So this
maximum noise level appears to be incorrectly attributed to the aircraft that was
operating within the large correlation circle.
Figure 5.24: Noise profile (left) and flight path (right) for a noise event that was attributed was
attributed to a Virgin Blue E-170 aircraft.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Event 4
Figure 5.25 shows the noise profile and flight path for the correlated noise event
identified as #4 on Figure 5.21. The aircraft in this instance was attributed to a DH8C
aircraft. The Lmax for this correlated noise event was 69.2 dB(A).
This event
highlights the difficulties that can occur when reviewing the data to remove those
which have been incorrectly attribute to aircraft. The noise profile is over a similar
time period and somewhat similar shape to that for an aircraft. However the track
clearly shows that the aircraft was headed well away from Hackett. As discussed in
Section 5.3 of this report on worse case aircraft noise events, a noise level around
70 dB(A) could be valid if the aircraft flew close to the NMT. This was clearly not the
case for this aircraft so the Lmax of 69.2 dB(A) appears to be incorrectly attributed to
an aircraft that was operating within the large correlation circle but far away from the
NMT.
Figure 5.25: Noise profile (left) and flight path (right) for a noise event that was attributed was
attributed to a DH8C aircraft.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Event 5
Figure 5.26 shows the noise profile and flight path for the correlated noise event
identified as #5 on Figure 5.21. The aircraft in this instance was attributed to a B737­
800 aircraft with Lmax of 65.2 dB(A). The profile does show an somewhat uneven
pattern but the time for the event is typical for an valid aircraft event and it is
reasonable that the Lmax for the aircraft could be near 65 dB(A).
Figure 5.26: Noise profile (left) and flight path (right) for a noise event that was attributed was
attributed to a B737-800 aircraft.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Event 6
Figure 5.27 shows the noise profile and flight path for the correlated noise event
identified as #6 on Figure 5.21. The aircraft in this instance was attributed to a B737­
800 aircraft with Lmax of 63.4 dB(A). The profile does show an somewhat uneven
pattern but the time for the event is typical for an valid aircraft event and it is
reasonable that the Lmax for the aircraft could be near 63 dB(A).
Figure 5.27: Noise profile (left) and flight path (right) for a noise event that was attributed was
attributed to a B737-800 aircraft.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
5.4.5.
High Noise Level Day in Second Quarter
The highest correlated noise event levels in the second quarter occurred on Tuesday
28/07/2009 and are shown in Figure 5.28. The noise profiles and flight paths for the
events with Lmax greater than 65 dB(A) were obtained from AsA. The two high noise
level events attributed to RPT aircraft are discussed below.
1
2
3
Figure 5.28: Lmax versus time of day for all the apparently correlated noise events on
28/07/2009.
Event1
Figure 5.29 shows the noise profile and flight path for the correlated noise event
identified as #1 on Figure 5.28. The event was attributed to a B737-400 aircraft with
Lmax of 87 dB(A). The duration of the noise event is comparable to what would be
expected for an RPT aircraft, although the profile does show a somewhat uneven
pattern. However the high value for Lmax appears incorrect as such a high level
Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
would only be expected for a high powered jet aircraft, such as an F-18 military
aircraft flying right over the NMT as discussed in Section 5.3. The track and the
details show that this was not the case so this is an incorrectly attributed Lmax .
Figure 5.29: Noise profile (left) and flight path (right) for a noise event that was attributed was
attributed to a B737-400 aircraft.
Event 3
Figure 5.17 shows the noise profile and flight path for the correlated noise event
identified as #3 on Figure 5.28. The aircraft in this instance was attributed to a DH8D
aircraft with Lmax of 67.7 dB(A). The duration of the noise event is comparable to
what would be expected for an RPT aircraft. However the profile does not show the
pattern that is typical for a valid aircraft event and the track shows the aircraft was
heading well away from North Canberra. Thus this can be considered to be an
incorrectly attributed Lmax .
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 5.30: Noise profile (left) and flight path (right) for a noise event that was attributed was
attributed to a DH8D aircraft.
5.4.6.
Comparison with Data from NMT near a Major Airport
From Figure 5.10, 5.12 and Figure 5.19, which show both the noise levels for the
apparently correlated RPT aircraft and all the noise events at the NMT, it can be
seen that the noise events correlated with aircraft tend to be ‘grouped’ in time
periods where there are a lot of community noise events around the same level. This
is more notable for the louder noise events, particularly those above 65 dB(A).
For comparison, Figure 5.31 shows a similar graph of correlated and uncorrelated
noise events typical day for the NMT at Leichhardt under the flight path for Sydney
airport. In such a location the levels from aircraft noise events are mainly above
70 dB(A) while those not attributed to aircraft are mostly less than 70 dB(A). This
indicates that the confidence in the accuracy of the correlated events from this
monitor at Leichhardt is higher than the level of confidence in the data from the NMT
in Hackett.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 5.31: Correlated noise events for a typical day at the Leichhardt NMT in Sydney. The
light blue squares are all the noise events while the red squares indicate a correlation with an
aircraft. It can be seen that majority of the correlated noise events are above 75 dB(A) ie well
above most of the local noise levels.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
5.5. Summary for RPT aircraft noise events
For this analysis, all aircraft that were turbo-prop or jet powered aircraft were
categorised as RPT aircraft as essentially all of these aircraft types are required to
follow standard departures and abide by the noise abatement procedures. After
removing clear multiple events from the correlated noise event data there were over
2,700 apparently correlated noise events during the 132 day summer period from
18/12/08 to 28/04/09. The distribution of potentially correlated RPT aircraft noise
events was found to be greater during the weekdays and greater during the peak
times for the airport operations.
Further analysis indicated that the data still contained noise events incorrectly
attributed to RPT aircraft. It was not practical to fully remove all these ‘false
positives’, nor all the events that were correctly correlated with RPT aircraft but with
incorrect noise levels. Consequently, it was decided to use samples of the first
quarter data set for detailed examination. These were:
a busy weekday;
a busy weekend day;
a day with the greatest number of apparently correlated noise events greater
than 70 dB(A) (a noisy weekday); and
cases of ‘worst case’ RPT aircraft noise events.
The data for the second quarter was reviewed and showed similar distribution of
RPT aircraft noise events. Samples selected from the second quarter data were:
a busy weekday; and
a day with the highest apparently correlated noise events.
Examples of ‘worst case’ noise levels for RPT aircraft could be found from three
flights which did not follow the standard departures and flew over the NMT in
Hackett. The Lmax values for these overflights ranged from 66 to 76 dB(A). It is
important to note that these direct overflights and non-compliance with the noise
abatement area only occur rarely and in this instance the cause was stormy weather
conditions. An extreme ‘worst case’ with Lmax values ranging from 82 to 90 dB(A)
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
noise level was found for F-18 overflights as part of the celebrations for Australia
Day. This was for a special celebratory event and the community should have
received a warning of the overflight.
A comparison of the distribution of the noise levels for two typical days from the first
quarter data is given in Table 5.3. While there is some doubt about the correct
attribution of noise levels to RPT aircraft, the analysis of the data does indicate that
the noise levels at Hackett due to standard RPT aircraft departures can be between
55 and 65 dB(A). However, it should be noted that there are many community noise
events with even higher noise levels.
Table 5.3 Distribution of RPT aircraft noise events for two typical days according to noise
level.
Range for Lmax, dB(A)
Potentially
RPT events
All noise
events
Friday 27/2/09
Potentially
RPT events
All noise
events
Saturday 3/1/09
Total > 55 dB(A)
36
260
15
162
55 to 60 dB(A)
22
179
8
107
60 to 65 dB(A)
13
67
7
41
65 to 70 dB(A)
1
9
0
11
70 to 75 dB(A)
0
4
0
2
>75 dB(A)
0
1
0
1
While the large correlation circle was useful for ensuring all aircraft flight paths were
captured but it resulted in a high number of false correlations. The loudest four
events on a day that appeared to be unusually noisy (Wednesday 07/01/09) showed
that the four above 66 dB(A) were uncharacteristic of aircraft noise events but rather
community noise events which occurred while the aircraft was somewhere within the
large correlation circle.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Except for the occasional non compliances due to adverse conditions or special
event flyovers, RPT aircraft follow the prescribed procedures. The resultant noise
levels, in terms of Lmax, at the NMT can be between 55 and 66 dB(A). Sampled
noise events from the NFPMS with Lmax values greater than 66 dB(A) were found to
be incorrectly attributed to aircraft.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
6. NOISE LEVELS FOR GENERAL AVIATION AIRCRAFT
6.1. General
This section discusses the correlated results from the noise monitor terminal due to
General Aviation (GA) aircraft.
For the analysis, all aircraft that were piston engined were categorised as General
Aviation (GA) aircraft. The term General Aviation is normally used to describe aircraft
operations other than scheduled airline flights and military operations. This could
include turbo-prop or jet aircraft provided they were not military aircraft or being
operated by an airline. The advantage in categorising all piston-engined, propeller
driven aircraft as GA aircraft was that the majority these aircraft types are below the
weight requirement for the noise abatement procedures (5700 kg maximum takeoff
weight) and therefore do not have to abide by the noise abatement procedures.
The data used to analyse GA aircraft noise events over the first quarter period was a
subset of the data set used for the investigation of the noise from RPT aircraft. The
smaller correlation circle that was centred on the noise monitor (shown in Figure 4.3)
was more suitable for more accurately capturing the noise from GA aircraft. The
larger correlation circle was found to falsely correlate too many community noise
events with aircraft that were within the large correlation circle but at a considerable
distance from the noise monitor.
The GA aircraft data using the smaller correlation circle was from 18/12/08 to
28/02/09. During this time, 420 noise events were recorded that could be attributed
to GA aircraft. This equates to an average of 5.75 potential aircraft noise events per
day above 55 dB(A). The data for February 2009 was used for the detailed analysis
for day of week, time of day and type of operation as it was exactly 4 weeks of noise
events over the summer period and outside any holiday periods. Where appropriate,
two sets of data are provided on the charts. The ‘unfiltered’ data is based on the
correlated noise events provided in the AsA data. As discussed in Section 4 of this
report, multiple noise events had been identified and these were removed from the
datasets. The ‘filtered’ data on these figures removes multiple correlations but may
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
still include some incorrect attributions to GA aircraft or incorrect noise levels for
correctly attributed GA aircraft.
The second quarter data was reviewed and showed similar trends to the data from
the first quarter. Selected individual higher noise events were further investigated.
6.2. Frequency of GA aircraft events
Figure 6.1 shows the distribution of the noise events in the subset from the first
quarter that were attributed to GA aircraft according to the hour of the day. The
shaded part of each bar represents the total number indicated in the original data
and the solid part the residual after the multiple events had been filtered out. This
figure shows a higher number of correlated GA aircraft noise events occurred
between 0900 and 1700 local time. This is as expected for a large proportion of GA
flights are for recreational or training purposes. Also, given that most recreational
pilots do not hold ratings to fly at night, night-time operations for GA aircraft are a
rare occurrence.
Figure 6.2 shows the distribution of correlated noise events for GA aircraft according
to the day of the week on which they occurred. This graph shows that the majority of
noise events due to non-jet aircraft occur on weekends. This is to be expected as
most GA aircraft are used for recreational flying and hence flying during working
hours is not as common as outside of working hours.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 6.1: Distribution of noise events attributed to GA aircraft, over the period from 01/02/09
to 28/02/09, according to the hour of the day during which they occurred.
Figure 6.2: Distribution of noise events attributed to GA aircraft, over the period from 01/02/09
to 28/02/09, according to the day of the week on which they occurred.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 6.3 shows the distribution of the recorded non-jet noise events according to
the type of operation being carried out by the GA aircraft. The majority of the noise
events come from non jet aircraft carrying out general operations. A “general”
operation is a flight that originates within the Canberra airspace and finishes within
the airspace. This classification includes aircraft carrying out circuits and city scenic
flights. The flyover operation designates aircraft that do not begin or end their flight
at Canberra Airport but only transit through the Canberra airspace.
Figure 6.3: Distribution of noise events attributed to GA aircraft, over the period from 01/02/09
to 28/02/09, according to the type of operation being carried out.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
6.3. Noise levels for GA aircraft events over the day
From inspection of the overall data from 18/12/08 to 28/02/09, two typical days were
chosen for detailed analysis. These were outside holiday periods; one was a busy
weekday, Friday 27/02/09, and the other was on a weekend, Saturday 28/02/09.
Figure 6.4 shows the noise levels for 9 potential GA aircraft noise events for Friday
27/02/09 having Lmax levels above 55 dB(A) with the loudest at 71.7 dB(A). For
comparison, Figure 6.5 shows a distribution of all the noise events recorded on the
same day. It can clearly be seen that there are many noise events throughout the
day with Lmax greater than 55 dB(A).
Figure 6.6 shows the noise levels for 14 potential GA aircraft noise events for
Saturday 28/02/09 with 3 events being greater than 65 dB(A). For comparison,
Figure 6.7 shows all of the noise events recorded by the NMT on the same day.
Again, this shows that there were many community noise events within and above
the same noise level range and these noise events occur well into the evening and
night time.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 6.4: Noise levels of potential GA aircraft noise events for Friday 27/02/09.
Figure 6.5: Noise levels for all noise events for Friday 27/02/09. The events potentially
correlated with a GA aircraft are labelled with black solid squares.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 6.6: Noise levels of potential GA aircraft noise events for Saturday 28/02/09.
Figure 6.7: Noise levels for all noise events for Saturday 28/02/09. The events potentially
correlated with a GA aircraft are labelled with black solid squares.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
6.4. Specific GA aircraft noise events
The preceding figures provide a general overview of the noise impact from GA
aircraft.
Some specific cases of GA aircraft noise events leading to the higher
values of Lmax will now be discussed.
6.4.1.
Helicopter overflights
A common concern expressed by residents was that they were subjected to high
noise impact from helicopters overflying the northern suburbs. Helicopters are not
required to comply with the noise abatement procedures unless they have a takeoff
weight greater than 5700kg. Residents had independently reported noise levels up
to 74 dB(A) for helicopters.
Several instances of helicopters were identified in the correlated data from AsA and
the specific noise profiles associated with these were sought. On 29/12/08 an event
attributed to a Bell 412 helicopter (Figure 6.8) had an Lmax of 74.6dB(A) with a
duration of 45 seconds. Figure 6.9 shows the noise versus time profile for this
event. The noise remains above 70 dB(A) for approximately 15 seconds, likely due
to the slow speed of the helicopter.
On 19/6/09 a noise event attributed to a helicopter had an Lmax of 80.7 dB(A) with a duration
of over 50 seconds. The noise profile and flight path for this event are shown in Figure 6.10
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 6.10. Full details of this event are not available due to security measures
applied to the flight path data.
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Independent Assessment of A
Aircraft
ircraft Noise in Hackett, ACT 30 March 20
2010
10
Figure 6.8: Image of a Be
Bell
ll 412
helicopter that caused th
the
e correlated
noise event shown in Fig
Figur
ure 6.9 [from
www.snowyhydrosouthcare.com.au].
www.snowyhydrosouthc
are.com.au].
Figure 6.9: Noise profile associ
associa
associated
ated
ted with the Bell 412 helicopter [from Airservice
Airservic
Airservices
es
s Australia].
Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 6.10: Example of a noise profile for a helicopter directly overflying the NMT on 19/6/09
with Lmax 80.7dB(A). Full details of this event are not available due to security measures
applied to the flight path data.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
6.4.2.
Incorrect noise level for GA aircraft overflight
The loudest recorded event apparently correlated to a GA aircraft occurred on
10/01/09 at 9:55am and had an Lmax of 86dB(A). This noise event was correlated
with a Cessna 172 type aircraft. The noise profile is shown in Figure 6.12 and is not
characteristic for such an aircraft.
Approximately
8 seconds from the
commencement of the event there is the maximum of 86dB(A) and then a sharp
drop. An FAA advisory circular [Federal Aviation Administration 2002] estimates the
noise level from a Cessna 172 aircraft during takeoff to be 63dB(A). From inspection
of the noise event profile it is suspected that the underlying noise profile that persists
after the 86dB(A) ‘spike’ could be due to the aircraft, with an Lmax of around 65dB(A)
which corresponds with the Federal Aviation Administration [2002] data for this type
of aircraft. For comparison a typical noise profile for a noise event considered to be
from a Cessna 150 aircraft overflying the NMT on 2/1/09 is shown in Figure 6.13.
Figure 6.11: Image of a Cessna 172 aircraft that was attributed to the noise event shown in
Figure 4.16 [reproduced with approval from © J. Gilbert, from Airliners.net].
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Figure 6.12: Noise profile of the noise event correlated with a Cessna 172 aircraft on the
10/01/09 at 9:55am.
Figure 6.13: Noise profile of a Cessna 150 aircraft on the 02/01/09 at 13:52. The Lmax for this
event was 65.8 dB(A).
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
6.5. Summary for GA aircraft Noise Events
For this analysis all aircraft that were piston engine, propeller driven aircraft were
categorised as General Aviation (GA) aircraft as these aircraft types are under
control in the airspace but are not required to follow standard departure procedures.
They are also generally below the weight required to comply with the noise
abatement procedures and the noise abatement area. They do need to comply with
the additional measures implemented by the airport to minimise aircraft noise over
the residential areas.
A small correlation circle was used in the analysis by AsA of a data set covering a 73
day period during the first quarter. Use of this data set minimised the number of
incorrect attributions for aircraft noise events. After removing clearly duplicate events
from the correlated noise event data there were 420 noise events correlated with GA
aircraft.
Further analysis indicated that the data still contained noise events
incorrectly attributed to GA aircraft. As it was not practical to investigate the detail of
every noise event, detailed analysis was undertaken for sample days and selected
events.
Most GA aircraft operate only during daylight and for the 73 day period there were
no correlated noise events during the night. The number of potentially correlated
noise events was greater during the weekends and distributed throughout the
daytime hours rather than during morning and evening peak as was the case for
RPT aircraft noise events.
The distribution of the noise levels for both correlated noise events and for all noise
events over a busy weekday and a busy weekend day are shown in Table 6.1. It can
be seen that the Lmax for the majority of the GA aircraft noise events, are between 55
and 65 dB(A) . Some can be up to 70 dB(A) and occasionally between 70 and 75
dB(A). Figure 6.14 shows the distribution of the Lmax for the GA aircraft noise events
the 73 day period in terms of the average per day. While there still remains some
doubt about the correct attribution of noise levels to GA aircraft, the analysis
indicates that frequency of the noise levels, in terms of Lmax, at Hackett due to GA
aircraft can be less than 2.4 per day between 60 and 65 dB(A), less than 0.6
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
between 65 and 70 dB(A) and less than 0.3 between 70 and 75 dB(A). Similar
distributions of the noise levels were found for GA aircraft noise events from a review
of the full first quarter and second quarter data.
Table 6.1: Distribution of GA aircraft noise levels for a day during the week and weekend.
Range for Lmax
Apparently
correlated GA
events
All noise
events
Apparently
correlated
GA events
Friday 27/2/09
All noise
events
Saturday 28/2/09
9
262
14
185
55 to 60 dB(A)
3
180
6
129
60 to 65 dB(A)
3
67
5
40
65 to 70 dB(A)
2
10
3
10
70 to 75 dB(A)
1
4
0
6
>75 dB(A)
0
1
0
0
Frequency of noise events (Per day occurane)
Total > 55 dB(A)
2.5
2
1.5
1
0.5
0
60-65
65-70
70-75
75-80
80-85
85-90
Noise Level (dBA)
Figure 6.14: Frequency per day of GA aircraft noise events over the 73 day analysis period.
This data may still be an overestimate as it may include incorrectly attributed data.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
7. AIRSERVICES
AUSTRALIA
QUARTERLY
REPORT
FOR
CANBERRA
The reports on the first and second quarters data for Canberra Hackett are available
on the AsA website [Airservices Australia 2009d, 2009f] and include the data
summaries and analysis by AsA for both the NMT at Jerrabomberra and at Hackett.
The NMT is monitoring the noise level continuously and this can provide valuable
information on the general noise environment as well as the aircraft noise events.
The AsA reports provide the average noise level over the quarters at Hackett and at
Jerrabomberra. These show the average noise levels at Hackett are about 5 dB(A)
less than at Jerrabomberra.
Hackett
Jerrabomberra
Quarter
Jan to April 2009
May to June 2009
Jan to April 2009
May to June 2009
Leq 24hr
49.4 dB(A)
48.8 dB(A)
54.3 dB(A)
55.8 dB(A)
Leq night
42.7 dB(A)
41.4 dB(A)
46.7 dB(A)
45.3 dB(A)
Over the two quarters that there were 4,621 and 5,340 apparently correlated noise
events at the Hackett NMT compared with 6,189 and 6,406 at the Jerrabomberra
NMT. The AsA report explains that the very large correlation circle for Hackett NMT
contributes to the likelihood of community noise events being incorrectly attributed to
aircraft.
AsA state that the 140 apparently correlated noise events in the first quarter with an
Lmax which equalled or exceeded 70 dB(A) at Hackett NMT were examined and
[Airservices Australia 2009d]:
“72% of these were events with multiple peaks in the noise recording which are
typical of community noise events. Note an aircraft noise event will have a
single peak. Given this, the N70 value for the Hackett monitor presented in
Table 1 should be considered an over-estimate and a more realistic statement
of the N70 value is at least 0.44 per day”
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
The second quarter report states there were 132 apparently correlated noise events
with an Lmax which equalled or exceeded 70 dB(A) and states [Airservices Australia
2009f]:
The N70 value detected at this monitor during the first quarter was affected by
the presence of community noise; 62.5% of the “aircraft noise events” over
70dB(A) detected by the Hackett monitor contain significant community noise.
Given this the best estimate of the N70 value is it is at least 0.56 events per
day
From the detailed analysis of the data sets by the AVU, and as discussed in the
previous sections of this report, it appears that even this estimate for the number
noise events over 70 dB(A) is an overestimate. Furthermore the AVU analysis
indicates that many of the apparently correlated noise events with Lmax between 55
and 70 dB(A) are also incorrect attributions to aircraft noise.
Appendix E of the AsA reports provides the mean Lmax aircraft noise levels for each
aircraft type based on all the apparently correlated aircraft noise events at the
Hackett NMT. Portion of this table from the first quarter report has been reproduced
as Table 7.1.
AsA acknowledges in their report that the data includes incorrectly attributed aircraft
noise events. However, even with this incorrect data included, it is interesting to
note from the stated mean maximum noise levels in the table that only two are
above 65 dB(A) and none above 70 dB(A). In comparison the mean maximum noise
levels at the Jerrabomberra NMT are all above 65 dB(A) with 5 aircraft types being
above 70 dB(A).
It is also interesting to note that the mean maximum noise levels for the RPT aircraft
are between 60 and 62 dB(A) and even with 1 standard deviation included are all
below 65 dB(A). This agrees with the detailed analysis on sample days undertaken
by the AVU (see section 6.3 of this report).
There is no comment in the AsA report but the high standard deviation of 13.8 dB(A)
for the Piper Chieftain/Navajo (PA31) warrants further investigation as this implies
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that there were some overflights by this aircraft type that were in excess of 80 dB(A).
The AVU examined the noise levels for this aircraft type in the data provided by AsA
and found that one of the seven apparently correlated noise events had an Lmax of
95 dB(A). This level is greater than for an F18 overflying the monitor so is clearly an
error in the data set. Removing this value reduced the average Lmax to 61.9 dB(A)
with a standard deviation of 6 dB. This is more in line with other GA aircraft types
shown in Table 7.1.
Similarly for the Piper PA 28A (second entry in Table 7.1), examination of the 16
apparently correlated noise events showed that one noise event had a level of
86 dB(A). Again this is a very uncharacteristic noise level for such an aircraft even if
it flew right over the NMT. Removal of this event reduced the average Lmax to
64 dB(A) with a standard deviation of 4.6 dB(A).
The mean maximum sound levels for all the correlated noise events in the second
quarter show similar results to the first quarter. In particular that the RPT aircraft
mean maximum noise levels are all below 65 dB(A).
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Table 7.1: Mean of the maximum aircraft noise levels at the Hackett Monitor for the first
quarter of 2009. [extracted from Appendix E of Airservices Australia 2009d]. The right column
lists the Mean Maximum Sound Level in dB(A) and Standard Deviation (in brackets).
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
8. AIRCRAFT NOISE IMPACT
As described in section 2.3 above, while the ANEF contours for assessing aircraft
noise impact may be a useful planning tool, but they do not give a direct indication of
the noise impact from aircraft operations. Away from the main flight paths and when
the noise is intermittent, alternative means need to be used for assessing the noise
impact.
The concern for the residents of Hackett is the intrusion of noise from
aircraft above the ambient or background noise level in the area and particularly at
night. The analysis in the previous sections of this report has shown that the Lmax
from aircraft can be above 55 dB(A). The Lmax for these aircraft are mainly in the 55
to 65 dB(A) range for RPT aircraft. A similar range of noise levels was found for
most of the GA aircraft with occasional overflights of low flying helicopters exceeding
70 dB(A). While the area is considered as a quiet residential area, the data has also
shown that during daytime there are many non aircraft events with noise levels
within and above those for aircraft noise events.
The noise mitigation measures and strategies currently implemented by the airport
result in no aircraft noise events in Hackett during the night time (2200-0600 hrs).
The NMT data shows that over the same period there are occasional non aircraft
noise events with Lmax between 55 and 60 dB(A) (for example see Figures 5.10,
5.12, 6.5 and 6.7).
Australian Standard 2021 on Aircraft noise intrusion [2000] provides guidance in
Table 3.3 for indoor design sound levels for house affected by aircraft noise. A
portion of this table is reproduced as Table 8.1. The noise level inside the residence
would depend on the reduction provided by the building enclosure. This reduction
could be between 15 dB for a lightweight construction with open windows and over
25 dB if the windows were closed. Thus an outside Lmax of 65 to 75 dB(A) could be
expected to be reduced to 50 dB(A) inside for open windows to closed windows.
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Table 8.1: Guidance for interior noise levels in terms of Lmax for aircraft noise reduction
[extracted from Table 3.3 of Australian Standard 2021, 2000.]
Research is ongoing into the field of disturbance due to aircraft noise at night. The
World Health Organisation (WHO) recommendations for community noise levels
[World Health Organisation 1999] included a table listing guidelines for a number of
specific environments and an extract is shown in Table 8.2:
Table 8.2: Guidelines for community noise in specific environments [extracted from Table 4.1
of World Health Organisation 1999.]
The guideline values in terms of Lmax of 45 dB(A) inside bedrooms can be compared
with the Australian Standard 2021 [2000] value of 50 dB(A). The corresponding
outside level of 60 dB(A) is based on an assumed 15 dB reduction by the building
enclosure with windows open.
The WHO has recently released a document on “Night Noise Guidelines For Europe”
[World Health Organisation 2009]. This proposes guidelines based on working group
reviews of the available scientific evidence on the health effects of night time noise.
The documents lists the following conclusions:
• Sleep is a biological necessity and disturbed sleep is associated with a number
of adverse impacts on health.
• There is sufficient evidence for biological effects of noise during sleep: increase
in heart rate, arousals, sleep stage changes and awakening.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
• There is sufficient evidence that night noise exposure causes self-reported sleep
disturbance, increase in medicine use, increase in body movements and
(environmental) insomnia.
• While noise-induced sleep disturbance is viewed as a health problem in itself
(environmental insomnia), it also leads to further consequences for health and
wellbeing.
• There is limited evidence that disturbed sleep causes fatigue, accidents and
reduced performance.
• There is limited evidence that noise at night causes hormone level changes and
clinical conditions such as cardiovascular illness, depression and other mental
illness. It should be stressed that a plausible biological model is available with
sufficient evidence for the elements of the causal chain.
The review concludes that Lnight,outside of 40 dB is equivalent to the lowest observed
adverse effect level (LOAEL) for night noise. It is important to note that this is the
averaged value over the night and not the maximum during an aircraft operation.
And the outside noise level is based on the windows being open so the reduction of
the building enclosure is only 15 dB. Over the range of Lnight,outside 40 to 55 dB the
report suggests that “diverse health effects are observed among the exposed
population. Many people have to adapt their lives to cope with the noise at night.
Vulnerable groups are more severely affected.” Lnight,outside of above 55 dB is
considered to be increasingly dangerous for public health..
The night noise guidelines in the WHO report are not given in terms of Lmax but in
terms of the noise level averaged over the night [World Health Organisation 2009]
and are given as:
Night noise guideline Lnight, outside of 40 dB(A) and
Interim target for Lnight, outside of 55 dB(A)
Short duration high noise level events would only increase the night noise level by a
small amount above the ambient. For example, a calculation can be made using a
model for the noise profile of an aircraft noise event with Lmax of 65 dB(A) and the
current night time noise level at Hackett of 42 dB(A) from AsA data. This shows that
it would need over 100 and 500 aircraft during the night each with Lmax of 65 dB(A) to
increase the Lnight, outside to 50 and 55 dB(A) respectively.
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
9. CONCLUDING SUMMARY
Aircraft operations
Both RPT and GA aircraft operate at Canberra Airport. The standard operating
procedures, noise abatement procedures and additional measures implemented by
the airport aim to minimise overflights of residential areas. Only occasionally due to
safety factors do RPT aircraft fly close to the residential area of Hackett. GA aircraft
are within air traffic control while they are near the suburban areas of North
Canberra but can overfly the northern suburbs and inner suburbs of Canberra.
Concerns about aircraft noise
There have been complaints about excessive aircraft noise from some residents in
North Canberra and in particular from those in Hackett and Watson. The residents
are particularly concerned about sleep disturbance from night time operations and
seek a formal night time curfew to be applied. A noise monitoring terminal (NMT)
was installed by AsA at Hackett in late December 2008 and the data for the first and
second quarters of 2009 has been published by AsA and has been examined by the
Acoustics and Vibration Unit (AVU).
Noise monitoring terminal
The identification of a noise event with an aircraft relies on the noise event meeting
the parameters set for the NMT and an aircraft being within a correlation circle
around the NMT. The installation at Hackett is challenging as the noise levels for
many aircraft events are similar to those for local noises. The initial analysis by the
AVU showed many cases of incorrectly attributed aircraft noise events and valid
aircraft noise events that were not correlated. Adjustments were made by AsA to the
settings and the correlation circle to try to overcome some of these problems.
Techniques were developed by the AVU to remove some clearly incorrect data.
However, the large correlation circle means that the data sets still include many
incorrectly attributed aircraft noise events. The noise level profile and flight path
would need to be examined for every correlated noise event to fully remove the
incorrect data.
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Regular Public Transport (RPT)
The initial analysis of the data for noise events for RPT aircraft involved removal of
multiple events from the data set. Further investigation indicated that the data still
contained incorrectly attributed noise events. As it was not practical to fully remove
all these ‘false positives’, or those with incorrect noise levels and samples of the data
were selected for detailed examination. These included:
a typical weekday;
a typical weekend day;
a day with the greatest number of apparently correlated noise events greater
than 70 dB(A) (a noisy weekday); and
cases of ‘worst case’ RPT aircraft noise events.
Examples of ‘worst case’ noise levels for RPT aircraft were found from three flights
which did not comply with the standard departures due to adverse conditions and
flew directly over the NMT in Hackett. The Lmax values for these overflights ranged
from 66 to 76 dB(A). An extreme ‘worst case’ with Lmax values ranging from 82 to
90 dB(A) occurred for F-18 overflights as part of the celebrations for Australia Day.
The detailed analysis for the four loudest event on a day that had the largest number
of higher noise events showed that the levels for the noise events with Lmax greater
than 66 dB(A) had been incorrectly attributed to aircraft. While there still remains
some doubt about the correct attribution of noise levels to RPT aircraft, the analysis
indicates that the noise levels at Hackett due to standard RPT aircraft departures
can be between 55 and 65 dB(A). It should be noted that there are many community
noise events with even higher noise levels during the day and evenings.
General Aviation
General Aviation (GA) aircraft are under direction from air traffic control in the
controlled airspace around the airport that extends beyond the Hackett area. They
are not required to follow the published standard departure procedures but are
directed by air traffic control while carrying out their desired operation (e.g. circuits,
city scenic flights). While GA aircraft are routed as much as possible over the non­
residential areas they do overfly the northern suburban areas of Canberra.
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After removing clear duplicate events from the correlated noise event data there
were 420 apparently correlated noise events over a 73 day period for the GA aircraft
data set with the smaller correlation circle and so less incorrect data. Most GA
aircraft operate only during daylight hours and there were no correlated noise events
during the night. The number of potentially correlated noise events was greater
during the weekends and distributed throughout the daytime hours rather than
occurring during morning and evening peak as was the case for RPT aircraft noise
events. As it was not practical to investigate the detail of every noise event to check
correct attribution, detailed analysis was undertaken for:
a busy weekday
a busy weekend
selected events including those related to helicopters
While there still remains some doubt about the correct attribution of noise levels to
GA aircraft, the analysis indicates that frequency of the noise levels at Hackett due
to GA aircraft can be less than 2.4 events per day between 60 and 65 dB(A), less
than 0.6 events between 65 and 70 dB(A) and less than 0.3 events between 70 and
75 dB(A). It should be noted that there is a greater incidence of non-aircraft noise
events with even higher noise levels during the day and evenings.
Airservices Australia Quarterly Report
The AsA Quarterly Reports for the periods January - March 2009 and April to June
2009 include the data summaries and analysis by AsA for the NMT at Hackett. The
reports acknowledge the likelihood of community noise events being incorrectly
attributed to aircraft. In their analysis AsA has removed some incorrect data and
conclude that the number of aircraft noise events greater than 70 dB(A) (N70) was at
least 0.44 and 0.56 events per day for the first and second quarters respectively.
From the detailed analysis of sub samples of the data set by the AVU, and as
discussed in the previous sections of this report, it appears that these are
overestimates for the N70. The AVU analysis has shown that RPT aircraft noise
N70 only occur occasionally when there is non compliance with noise abatement
procedures. Such direct flyovers of the residential areas are usually due to safety
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
issues or for special event celebrations.
The AVU analysis for GA aircraft has
indicated a N70 of less than 0.3 events per day.
The listing of mean Lmax aircraft noise levels for each aircraft type shows only two
GA aircraft types with levels just over 65 dB(A). AVU analysis has shown that the
mean values include data for incorrectly attributed aircraft and after reanalysis all the
mean Lmax aircraft noise levels are less than 65dB(A).
Aircraft noise impact
A major concern of the Hackett residents is that increased night time aircraft
operations would lead to excessive noise intrusion and sleep disturbance. and there
are no clear criteria nationally or internationally.
The guideline from Australian
Standard 2021 [2000] is that the Lmax, inside the bedroom should not exceed
50 dB(A). An average value of attenuation for a residential building depends on the
construction but can be assumed to be between 15 and 25 dB for open and closed
windows respectively. Thus an outside Lmax of 65 to 75 dB(A) could be expected to
be reduced to 50 dB(A) inside for open and closed windows respectively.
The World Health Organisation (WHO) recommendations for community noise levels
[World Health Organisation 1999] included a table listing guidelines for a number of
specific environments. The guideline for Lmax inside bedrooms of 45 dB(A)can be
compared with the Australian Standard 2021 [2000] value of 50 dB(A).
The
corresponding outside guideline of 60 dB(A) is based on assumed 15 dB reduction
by the building enclosure with windows open.
The recent WHO document on “Night Noise Guidelines For Europe” [World Health
Organisation 2009]. This proposes guidelines based on the health effects of night
time noise which are not given in terms of Lmax but in terms of the noise level
averaged over the night. The guideline and target levels assuming open windows,
for Lnight, outside are 40 and 55 dB(A) respectively. The AsA data shows that the current
Lnight,outside at the NMT is around 42 dB(A). Simple modelling shows that it would
need over 100 and 500 aircraft during the night each with Lmax of 65 dB(A) to
increase the Lnight, outside to 50 and 55 dB(A) respectively.
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10.
REFERENCES
Airservices Australia, 2008a Noise and Flight Path Monitoring System Canberra
Quarterly
Report
October
-
December
available
2008
from
http://www.airservices.gov.au/projectsservices/reports/nfpms/2008/CB08Q4.pdf
Airservices Australia, 2008b. Flying Around Visual Guide. [Online]. Available at
www.airservices.gov.au/pilotcentre/training/flyingaround/viewer/MapLoader.asp.
Airservices Australia, 2008c. Noise and Flight Path Monitoring System. Available
from www.airservices.gov.au/projectsservices/reports/nfpms/.
Airservices
Australia,
2009c.
Webtrak.
[Online]
Available
from
www.airservicesaustralia.com/aviationenvironment/noise/webtrak/info.asp.
Airservices Australia, 2009d. Noise and Flight Path Monitoring System Canberra
Quarterly
Report
January
-
March
2009
available
from
http://www.airservices.gov.au/projectsservices/reports/nfpms/2009/CB09Q1.pdf.
Airservices Australia, 2009e Departures and Arrival Procedures, Airservices [DAP].
Airservices Australia, 2009f. Noise and Flight Path Monitoring System Canberra
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April
to
June
2009
available
from
http://www.airservices.gov.au/projectsservices/reports/nfpms/2009/CB09Q2.pdf.
Australian Standard AS 2021 – 2000, Acoustics Aircraft noise intrusion – Building
siting and construction, Standards Australia
Canberra
Airport,
2009a,
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event
noise
exposure
contours
www.canberraairport.com.au/air_noise/noise_describing.cfm#3 [viewed June 2009]
Canberra
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Airport
Master
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www.canberraairport.com.au/pdf/masterplan2005.pdf.
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http://www.canberraairport.com.au/air_noise/noise_minimising.cfm,
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noise.
viewed
2009
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Independent Assessment of Aircraft Noise in Hackett, ACT 30 March 2010
Canberra Airport, 2009c. Canberra Airport Preliminary Draft Master plan. Accessed
at www.canberraairport.com.au/PDF/masterplan/CA_MST2009_Chap14.pdf. viewed
August 2009
Curfew4Canberra, 2008 Online. Available from www.curfew4canberra.org.au/
viewed August 2009
Federal Aviation Administration, 2002. Estimated Airplane Noise Levels in A-
Weighted Decibels, FAA AC No. 36-3H.
World
Health
Organisation,
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for
Community
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Noise
Guidelines
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Europe