202 Uxbridge Road
London
W12 7JP
Tel: +44(0)203 475 2280
Fax: +44(0)203 475 2281
info@clementacoustics.co.uk
www.clementacoustics.co.uk
PROPOSED NURSERY, 4 HOLM LANE, BIRKENHEAD
NOISE IMPACT ASSESSMENT
Report 7522-NIA-01-RevC
Prepared on 11 January 2013
Issued For:
Graham Smith
3 Croft Drive
West Caldy
Wirral
CH48 2JG
Contents
1.0
INTRODUCTION .......................................................................................................................... 1
2.0
SITE DESCRIPTION ...................................................................................................................... 1
3.0
ENVIRONMENTAL NOISE SURVEY .............................................................................................. 1
3.1
3.2
Procedure ......................................................................................................................................... 1
Equipment ........................................................................................................................................ 2
4.0
RESULTS ...................................................................................................................................... 2
4.1
Environmental Noise Time History ................................................................................................... 2
5.0
NOISE EMISSIONS CRITERIA ....................................................................................................... 3
6.0
DISCUSSION ................................................................................................................................ 3
6.1
6.2
Source Noise From Children Playing On A Soft Play Area................................................................. 3
Noise Impact Assessment ................................................................................................................. 4
7.0
CONCLUSION .............................................................................................................................. 6
List of Attachments
7522-SP1-RevA
7522-TH1
Appendix A
Appendix B-RevB
Indicative Site Plans
Environmental Noise Time History
Glossary of Acoustic Terminology
Acoustic Calculations
Ref: 7522-NIA-01-RevC
10 January 2013
1.0
INTRODUCTION
Clement Acoustics Ltd has been commissioned by Graham Smith, 3 Croft Drive, West Caldy, Wirral,
CH48 2JG to investigate and assess the noise impact from a proposed children’s day nursery at
4 Holm Lane, Prenton, Birkenhead, Wirral, Merseyside, CH43 2HP on nearby residential properties.
This report presents the results of a background noise survey and assessment of nursery
playground noise emissions and outlines any necessary mitigation measures.
2.0
SITE DESCRIPTION
Current proposals are to construct a children’s day nursery on the site at 4 Holm Lane. The
proposed nursery will have a soft play area at the rear of the property. Concerns have been raised
over the transference of noise emanating from the proposed play area to nearby residential
receivers. The proposed property is bounded by Woodbine Cottage to the East, Holmside Lane to
the South, Holm Lane to the West and No.8 Holm Lane to the North.
As the windows facing onto the nearby noise sensitive receivers of the proposed nursery will not be
openable we would anticipate that the main source of noise disturbance would emanate from
children playing in the rear play area.
The closest affected residential receivers are the bungalow of No.8 Holm Lane located
approximately 6m from the centre of the proposed play area and Woodbine Cottage located
approximately 11m from the centre of the proposed play area.
3.0
ENVIRONMENTAL NOISE SURVEY
3.1
Procedure
In order to assess existing background noise levels in the area, an environmental noise survey was
undertaken over a daytime period at the position marked on indicative site plan 7522-SP1.
This position was chosen to monitor noise levels representative of those currently affecting the
closest residential premises.
7522: PROPOSED NURSERY, 4 HOLM LANE, BIRKENHEAD
Noise Impact Assessment
Page 1 of 6
Ref: 7522-NIA-01-RevC
10 January 2013
Continuous automated monitoring was undertaken for the duration of the survey between 11:50
and 14:50 on 4 September 2012. Weather during the survey was dry with light winds, therefore
suitable for measurement of environmental noise.
The measurement procedure generally complied with BS7445:1991. Description and measurement
of environmental noise, Part 2- Acquisition of data pertinent to land use.
3.2
Equipment
The equipment calibration was verified before and after use and no abnormalities were observed.
The equipment used was as follows:
•
1 No. Svantek Type 957 Class 1 Sound Level Meter
•
Norsonic Type 1251 Class 1 Calibrator
4.0
RESULTS
4.1
Environmental Noise Time History
The LAeq: 5min, LAmax: 5min, LA10: 5min and LA90: 5min acoustic parameters were measured and are shown as a
time history in Figure 7522-TH1.
Background noise levels were dominated by traffic noise from Holm Lane, the A552 and other
surrounding roads.
Average ambient and minimum background noise levels for the measurement period are shown in
Table 4.1.
Average ambient noise level
Minimum background noise level
LAeq: 5min dB(A)
LA90: 5min dB(A)
51
43
Typical Daytime Hours
[11:50 - 14:50]
Table 4.1: Average ambient and minimum background noise levels
7522: PROPOSED NURSERY, 4 HOLM LANE, BIRKENHEAD
Noise Impact Assessment
Page 2 of 6
Ref: 7522-NIA-01-RevC
10 January 2013
5.0
NOISE EMISSIONS CRITERIA
Although primarily used for assessing noise emissions of industrial activities, British
Standard 4142:1997 can be seen as a good guide for assessing the suitability of noise emissions to
residential receivers. In a BS4142 assessment, corrections are applied to measured noise levels in
order to calculate a noise rating level for the effects of the source on nearby noise sensitive
receivers.
BS4142:1997:’Method for rating industrial noise affecting mixed residential and industrial areas’
states that a noise rating 5dB above the background noise level is of ‘marginal significance’. If the
difference is of 10dB or more, then there is an indication that ‘complaints are likely’. A noise rating
level of 10dB below the existing background noise is defined as ‘a positive indication that
complaints are unlikely’.
The proposed Nursery will only be open Monday – Friday and will at no time be open at the
weekends or on public holidays. The play area will only be in use between the hours of 09:00-16:30,
therefore noise rating levels will be compared against the minimum measured background noise
level of 43 dB(A).
6.0
DISCUSSION
6.1
Source Noise From Children Playing On A Soft Play Area
Manual measurements of children playing on a soft play area were undertaken at a similar nearby
day nursery. Measurements where conducted at a distance of 1m from a group of 12 children
between 3 and 4 years of age playing continuously for 15 minutes. At the time of conducting the
survey it had been advised that the maximum allowable number of children permitted to play
within the proposed rear yard would be 12.
Subsequent changes to the proposals are to ensure no more than 10 children are permitted on the
soft external play area per session. Measurements encapsulate the oldest and subsequently most
active children of the nursery at play and consequently are representative of worst case noise levels
expected at the proposed day nursery.
7522: PROPOSED NURSERY, 4 HOLM LANE, BIRKENHEAD
Noise Impact Assessment
Page 3 of 6
Ref: 7522-NIA-01-RevC
10 January 2013
Noise emissions from the group of children playing on a soft play area correspond to a typical time
averaged sound pressure level of 64 dB(A) at 1 metre.
In order to calculate worst case noise emissions at the nearest residential receivers, a worst case
scenario has been modelled assuming the play area at capacity with the oldest children playing
continuously for a one hour period.
Further proposals have been made to include a canopy roof within the secure play area that will
extend a distance of 6m from east boundary façade of the proposed nursery. The canopy roof will
be set at a height of 2.2m from ground level.
The attached site plan 7522-SP1-RevA shows the proposed soft play area location as well as the
nearby residential receiver locations.
6.2
Noise Impact Assessment
Taking all necessary acoustic corrections into account, including distance losses and screening due
to a proposed boundary wall, noise emissions levels at identified noise sensitive receivers would be
as shown in Table 6.1, with detailed calculations shown in Appendix B-RevB.
A 5dB penalty has been added in order to account for the distinct nature of the source noise as
specified in BS4142:1997.
Receiver
Calculated Noise
Rating Level at
Receiver
LAeq,1hr
Measured Minimum
Background Noise
[Daytime Period]
LA90,5mins
Difference
Indication
Receiver 1:
Woodbine Cottage
46 dB(A)
43 dB(A)
+ 3 dB
Marginal Significance
Receiver 2:
No.8 Holm Lane
39 dB(A)
43 dB(A)
- 4 dB
Complaints Unlikley
Table 6.1 Noise rating level and assessment for residential receivers
As shown in Table 6.1, worst case noise emission levels at Receiver 1 would be expected to be of
‘Marginal Significance’ and noise emission levels at Receiver 2 would be closer to the region where
noise emissions are specified as ‘Complaints would be unlikely’.
7522: PROPOSED NURSERY, 4 HOLM LANE, BIRKENHEAD
Noise Impact Assessment
Page 4 of 6
Ref: 7522-NIA-01-RevC
10 January 2013
It should be noted that children would not be playing within the soft play area during night-time
hours, over the weekend period or on public holidays, which is when complaints due to noise are
more likely to occur.
Dependent on the location of the children within the proposed play area, potential additional
mitigation measures owing to the transference of noise between the source and receivers may be
considered. In the instance of children playing near to the perimeter of the boundary wall,
screening from the walls and adjacent garage building to the nearby noise sensitive receivers
specifically those of Woodbine Cottage, will offer a higher degree of screening and consequent
reduction to the calculated noise rating level at the receiver.
Children playing nearer the proposed nursery building may retain a line of sight with the first floor
window of Woodbine Cottage. However, it should be noted that there would be an increase to the
distance attenuation between the source and receiver and that the intermittent garage between
the two properties would provide a degree of screening due to the child’s height.
Further consideration should be made to the mitigation of noise offered by the inclusion of the
canopy shown in indicative site plan 7522-SP-RevA. Due to the height of the canopy being below
that of the perimeter wall, children playing beneath the canopy will subsequently be screened from
view of the nearby noise sensitive receiver of Woodbine Cottage and therefore eradicate a line of
sight to this receiver. As such we would expect the noise arising from children playing beneath the
canopy to be significantly lower than those with a direct line of sight to the nearby noise sensitive
receivers. As our noise source is not fixed there is inherent difficulty in quantifying the overall noise
mitigation offered by the proposed canopy on predicted noise levels shown in Table 6.1. It can
however, be assumed that a barrier that reduces the line of sight between source and receiver
should offer a minimum attenuation of 5dB.
An impact assessment of ‘marginal significance’ at Receiver 1 has been based on a worst case
scenario of the play area at capacity with all children in direct line of sight of the noise sensitive
window on the first floor of the property. It should be noted that an applied 5dB penalty has been
added in order to account for the distinct nature of the source noise as specified in BS4142:1997
but that without this penalty applied noise levels would indicate that ‘complaints would be unlikely’
at Receiver 1.
7522: PROPOSED NURSERY, 4 HOLM LANE, BIRKENHEAD
Noise Impact Assessment
Page 5 of 6
Ref: 7522-NIA-01-RevC
10 January 2013
7.0
CONCLUSION
A noise survey has been undertaken at a proposed children’s day nursery at 4 Holm Lane, Prenton,
Birkenhead, Wirral, Merseyside, CH43 2HP. The results of the survey have enabled the assessment
of noise propagation of children’s play activity to the nearest noise sensitive receivers.
Calculations have shown that noise emissions at Receiver 1 would be expected to be of ‘Marginal
Significance’ and noise emission levels at Receiver 2 would indicate that ‘Complaints would be
unlikely’.
Outline mitigation advice has been suggested on the basis of a worst case scenario assessment.
Report by
Checked by
Nicholas Dobbs AMIOA
Duncan Martin MIOA
7522: PROPOSED NURSERY, 4 HOLM LANE, BIRKENHEAD
Noise Impact Assessment
Page 6 of 6
Proposed Nursery
Play Area
Holmside Lane
Proposed Canopy
Proposed Perimeter Wall
7522-SP1-RevA Indicative site plan showing noise monitoring position and nearest noise sensitive receivers
Holm Lane
No.8
Woodside Cottage
Date: 11 January 2013
Noise Survey Position
Noise Sensitive Receiver
7522-TH1
Level (dB re 2x10-5 Pa)
0
10
20
30
40
50
60
70
80
90
LAeq
Lamax
LA10
Environmental Noise Time History
4 September 2012
4 HOLM LANE, PRENTON
LA90
APPENDIX A
GLOSSARY OF ACOUSTIC TERMINOLOGY
dB(A)
The human ear is less sensitive to low (below 125Hz) and high (above 16kHz) frequency sounds. A
sound level meter duplicates the ear’s variable sensitivity to sound of different frequencies. This is
achieved by building a filter into the instrument with a similar frequency response to that of the ear.
This is called an A-weighting filter. Measurements of sound made with this filter are called Aweighted sound level measurements and the unit is dB(A).
Leq
The sound from noise sources often fluctuates widely during a given period of time. An average
value can be measured, the equivalent sound pressure level Leq. The Leq is the equivalent sound level
which would deliver the same sound energy as the actual fluctuating sound measured in the same
time period.
L10
This is the level exceeded for not more than 10% of the time. This parameter is often used as a “not
to exceed” criterion for noise
L90
This is the level exceeded for not more than 90% of the time. This parameter is often used as a
descriptor of “background noise” for environmental impact studies.
Lmax
This is the maximum sound pressure level that has been measured over a period.
Octave Bands
In order to completely determine the composition of a sound it is necessary to determine the sound
level at each frequency individually. Usually, values are stated in octave bands. The audible
frequency region is divided into 10 such octave bands whose centre frequencies are defined in
accordance with international standards.
Addition of noise from several sources
Noise from different sound sources combines to produce a sound level higher than that from any
individual source. Two equally intense sound sources operating together produce a sound level
which is 3dB higher than one alone and 10 sources produce a 10dB higher sound level.
Glossary of Acoustic Terminology
Page 1 of 2
CLEMENT ACOUSTICS
APPENDIX A
Attenuation by distance
Sound which propagates from a point source in free air attenuates by 6dB for each doubling of
distance from the noise source. Sound energy from line sources (e.g. stream of cars) drops off by
3dB for each doubling of distance.
Subjective impression of noise
Sound intensity is not perceived directly at the ear; rather it is transferred by the complex hearing
mechanism to the brain where acoustic sensations can be interpreted as loudness. This makes
hearing perception highly individualised. Sensitivity to noise also depends on frequency content,
time of occurrence, duration of sound and psychological factors such as emotion and expectations.
The following table is a reasonable guide to help explain increases or decreases in sound levels for
many acoustic scenarios.
Change in sound level (dB)
1
3
6
10
20
Change in perceived loudness
Imperceptible
Just barely perceptible
Clearly noticeable
About twice as loud
About 4 times as loud
Barriers
Outdoor barriers can be used to reduce environmental noises, such as traffic noise. The
effectiveness of barriers is dependent on factors such as its distance from the noise source and the
receiver, its height and its construction.
Reverberation control
When sound falls on the surfaces of a room, part of its energy is absorbed and part is reflected back
into the room. The amount of reflected sound defines the reverberation of a room, a characteristic
that is critical for spaces of different uses as it can affect the quality of audio signals such as speech
or music. Excess reverberation in a room can be controlled by the effective use of sound-absorbing
treatment on the surfaces, such as fibrous ceiling boards, curtains and carpets.
Glossary of Acoustic Terminology
Page 2 of 2
APPENDIX B-RevB
7522
4 HOLM LANE, BIRKENHEAD
APPENDIX B.1 RECEIVER 1 ASSESSMENT
Receiver: Woodbine Cottage
Source: Noise from 12 Children playing on soft play area
Frequency, Hz
500
1k
63
125
250
External Sound Pressure Level
Children Playing on Soft Area
2k
4k
8k
dB(A)
60
58
55
59
60
59
51
41
64
Distance correction (11m)
-21
-21
-21
-21
-21
-21
-21
-21
Attenuation provided by screening of intermediate wall, dB
0
0
0
-1
-2
-3
-5
-5
Correction for tonal / distinguishable noise emissions
5
5
5
5
5
5
5
5
Sound pressure level at receiver
44
42
39
42
42
40
30
20
Minimum Measured Daytime LA90
46
43
APPENDIX B.2 RECEIVER 2 ASSESSMENT
Receiver: No.8 Holm Lane
Source: Noise from 12 Children playing on soft play area
Frequency, Hz
500
1k
63
125
250
External Sound Pressure Level
Children Playing on Soft Area
2k
4k
8k
dB(A)
60
58
55
59
60
59
51
41
64
Distance correction (6m)
-16
-16
-16
-16
-16
-16
-16
-16
Attenuation provided by screening of intermediate wall, dB
-6
-8
-10
-12
-15
-15
-15
-15
Correction for tonal / distinguishable noise emissions
5
5
5
5
5
5
5
5
Sound pressure level at receiver
43
39
34
36
34
33
25
15
Minimum Measured Daytime LA90
39
43