Environmental Monitoring
& Technology Series
Noise monitoring &
evaluation
For Technicians
Study module 4
Measuring noise
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Noise monitoring & evaluation
Study Module 4
Assessment details
Purpose
This unit of competency covers the ability to monitor noise using handheld sound level
meters and fixed sound monitoring stations with either data logging or telemetry. It includes
the ability to perform noise surveys, process data and report results in accordance with
enterprise standards.
Instructions
◗ Read the theory section to understand the topic.
◗ Complete the Student Declaration below prior to starting.
◗ Attempt to answer the questions and perform any associated tasks.
◗ Email, phone, book appointment or otherwise ask your teacher for help if required.
◗ When completed, submit task by email using rules found on last page.
Student declaration
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Details
Student name
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Assessor
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Class code
NME
Assessment name
SM4
Due Date
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Total Marks Available
59
Marks Gained
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Final Mark (%)
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Date Marked
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Weighting
This is one of six formative assessments and contributes 10% of
the overall mark for this unit
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Introduction
So far, we have learnt what sound is, the physical properties of sound, how we hear sound,
how sound travels and how we represent sound through the different stages of sound
propagation and travel from the source to the receiver. But how exactly do we measure it?
A quick recap of what we know;
The source of the sound, or emission, is measured absolutely as sound power in unit Watts,
but expressed as a sound power level relative to the 1E-12 Watts reference.
The travelling sound waves, or immission, is measured absolutely as sound pressure in unit
Pascal but expressed as a sound pressure level relative to the 2E-5 Pascal reference.
The surface of the immission sound wave field is measured absolutely as intensity in Watts
per meter squared but relatively as sound intensity level relative to 1E-12 W reference.
The sound pressure received by the ear, exposure or dose, is measured absolutely as Pascals
squared times time (Pa2.h), but expressed as sound exposure level as decibels.
This is a lot of information, fortunately for the environmental technician, we can (in most
cases) either get away without measuring all of these aspects, or we can use just one or two
pieces in equipment.
Types of sound measurement devices
The different types of measuring device are classified based on what they actually measure
but generally speaking, we have Sound Level Meters (SLM), Sound Intensity Probes (SIP) and
personal sound exposure meters (PSEM). Of key importance to this unit of competence is
the Sound Level meter.
Sound Level Meters (SLM)
The SLM is the key device used by environmental and WHS field technicians (in conjunction
with a data logging versions for field studies). These devices form the major part of these
notes so won’t be discussed here in any great detail.
Data loggers
A data logger is a device that captures data. For our purposes, it is an ugly computer that
requires another computer to read it! The point of a data logger is space, as in space for the
data, they also need to be very rugged to put out in the field.
Data loggers are designed to monitor noise levels in remote or unattended environment for
long periods of time (say, for periods of up to 2 weeks). The internal computer of the data
logger will typically compute the same measurements as the handheld instruments
including percentile noise statistics as well as the equivalent noise levels for time intervals
ranging from one minute to one hour (typically 15 minutes). Modern data loggers can also
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operate as a sound level meter as they display the current noise level on either the loggers
LCD screen or a connected PC. You will explore data loggers more in later modules.
Sound Intensity Probes (SIP)
These are very specific probes that are used to determine many qualities of sound such as
sound power requirements emitted from machinery, or to determine the source of a noise.
Although, formally speaking, sound intensity is the product of sound pressure and particle
velocity, we have ignored the particle velocity concept as it has little relevance to the field
technician, but massive relevance to the overall filed of acoustics.
Commonly, there are two different probe set-ups used in sound intensity measurements,
but all set-ups use probes that measure the sound intensity using two microphones.
The p-p type of sound intensity probe measures the sound intensity using two phasematched microphones positioned face-to-face with a known distance between them. These
microphones determine a pressure gradient, from which the particle velocity is calculated.
The sound pressure is determined from the average from both microphones output.
The p-u type of sound intensity probe measures both the sound pressure with a microphone
and the particle velocity directly with a particle velocity probe.
Figure 4.1 – Example of a SIP [source]
Personal Sound Exposure Meters (PSEM)
Another common sound or noise measurement device is the Personal Sound Exposure
Meter or PSEM. The latest version of these things are literally tiny little ‘badges’ that people
wear during their working day.
The PSEM has, like all technology, undergone significant change throughout its relatively
short history, and they used to be clunky devices hooked on to your belt, with a microphone
on a cable was pinned to your collar to receive noise as close to your ear as possible.
You will learn more about the PSEM in the next module where noise studies are applied to
the Workplace Health & Safety environment.
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Industry standards
The practice of noise measurements is both heavily regulated and standardised. As
mentioned several times, the reason for the regulation is to protect human hearing and loss
of amenity. Standardisation (i.e. the use of the same techniques worldwide) is a result of the
physical nature of sound (it is a universal property) and is and the requirement for results to
be reportable in similar units worldwide.
Sound measurements can be done for a variety of reasons, but generally they can be
qualitative (informative) or quantitative (legal). For this reason, different classes or types of
noise measurement equipment have been developed.
Australian & International Standards
In Australia, we use the Australian Standard series of documents (from Standards Australia)
which cover three main areas of implementation and monitoring;
Compliance requirements of equipment
All acoustic equipment is designed in accordance with the International Electrotechnical
Commission (IEC) specifications (or equivalent). The IEC develop the ‘overarching’ electrical
standards for most of the electrical equipment used worldwide and is heavily involved in
standardising the electrical function and calibration of noise monitoring equipment.
Workplace health and safety
The series of standards that apply in Australia for workplace monitoring of noise is the
AS/NZS1269:2005 series, with standard 1 being the most significant as it deals with the
operational aspects of the monitoring. This forms the majority of the next module.
Environmental
The Australian Standard for environmental monitoring of noise is covered by the AS 1055:13 series. Note that there are many other non-regulatory documents used in environmental
monitoring but these are dealt with by module 6.
Legal categories of instrument
Unfortunately even with standardisation, there is a multitude of different terms for the
same thing as a result of ‘sovereign differences’, but the only two legal classifications we
need to worry about is the qualitative and quantitative classes, which are explained below;
◗ Type 0 equipment
(factory calibration and the like)
◗ Class 1 / Type 1 SLM
(high accuracy and precision, for legal use)
◗ Class 2 / Type 2 SLM
(lower accuracy and precision, for common use)
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The Integrated Averaging Sound Level Meter (IASLM)
What is a Sound Level Meter (SLM)?
A Sound Level Meter (SLM) is a measurement device used to measure various properties of
sound waves that enables us to relate the measured property for either the protection of
hearing (WHS applications) or the protection of loss of amenity (community and
environmental applications). A typical Class 1 / Type 1 SLM can be seen in figure 4.2 below;
Figure 4.2 – Typical Sound Level meter (SLM). This is a Bruel & Kjaer model.
These types of meters are typically classified as Class 1 / Type 1 sound level meters. We
know it is a SLM, so it measures the sound pressure from a source, but what do the other
terms mean?
Integration is a mathematical term which implies that the area under a curve is calculated.
In our case, the curve is created as a graph of the sound pressure versus frequency, so it is
the frequency domain that is integrated. The specific area calculated varies depending on
how the frequency octaves are used (1/1 octave or 1/3 octaves).
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Averaging is applied to the decibels in the time domain (from a graph of decibels versus
time or frequency) and is typically performed early in the electrical process by use of a Root
Mean Square (RMS) circuit. You will learn about this circuit later. The typical electrical
‘process’ that occurs in a IASLM can be seen in figure 4.5 below;
Figure 4.3 – Construction of a typical Sound Level Meter (Rion NA 27 SLM).
Admittedly, this looks a little confusing, but the whole process can be broken down into its
key constituents (which are listed below and explained in the following sections);
◗ Microphone receives sound pressure and converts to electrical signal
◗ Signal is pre-amplified (sometimes more than once, depending on the instrument)
◗ Frequency weighting is applied (or not, if linear pass (un-weighted) is requested)
◗ Analogue to digital signal conversion occurs
◗ Digital signal processing to determine RMS sound pressure occurs
◗ Digital signal processing of frequency analysis occurs
◗ Displaying the final information on the readout
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The microphone
When an object vibrates in the presence of air, the air molecules at the surface will begin to
vibrate, and this vibration will travel through the air as oscillating pressure waves at
frequencies and amplitudes determined by the original sound source power. Microphones
are mechanical transducers that are designed, like the human ear, to transform pressure
waves into useful electrical signals which we can use to determine the properties of the
sounds. Like the human ear, microphones are designed to measure a very large range of
amplitudes, typically measured in decibels (dB) and frequencies in hertz (Hz).
Microphone type & construction
Measurements of sound pressure level can be carried out with a variety of microphone
types. Most IASLM’s employ the condenser microphones because they are compact and
delivers stable and reliable response, but other microphone types (such as resistance) are
sometimes used.
A condenser microphone is a type of ‘capacitance’ microphone. The housing of a condenser
microphone utilises basic transduction principles to transform the sound pressure to
capacitance variations, which are then converted to an electrical voltage. This is
accomplished by taking a small thin diaphragm and stretching it a small distance away from
an insulated stationary metal backplate. A voltage is applied to the backplate to form a prepolarised capacitor by using an electret plate with permanently charged particles attached
to the backplate.
In the presence of oscillating pressure, the diaphragm will move which changes the gap
between the diaphragm and the backplate. Using a load resistor, this produces an oscillating
voltage from the capacitor, proportional to the original pressure oscillation.
Figure 4.4 – Construction of a typical SLM condenser microphone (RION NA 27)
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Microphone characteristics
The key operational characteristics of microphones used for SLM’s define the responses of
the microphone and are directly related to the quality of the transduced sound pressure.
The key characteristics for IASLM include the frequency response characteristics, the
directional characteristics, the thermal characteristics and the humidity characteristics.
The frequency response as well as the temperature and humidity characteristics of a prepolarized microphone depend considerably on the type and properties of the materials
used. The frequency range is determined by the resonance frequency of the diaphragm
assembly.
Voltage Amplification
The voltage generated from the microphone is incredibly small, so small in fact that it has
little practical purpose, and therefore it requires ‘enlarging’ so that a practical voltage is
achieved for use by later componentry. This process is called amplification.
Preamplifier
Since the condenser microphone is a small-capacity transducer, it has high impedance,
especially at low frequencies. Therefore a very high load resistance is required to ensure
uniform response extending to the low frequency range. The relationship between the
microphone capacitance and the low-range cut-off frequency can be expressed as follows.
If the output of the microphone were directly routed through a long shielded cable, the
capacitance between the cable conductors would cause a sharp drop in sensitivity, as is
evident from the following equation.
For the above reasons, a preamplifier is connected directly after the microphone, to provide
a low-impedance output signal. To reduce measurement deviations due to refraction effects
and the acoustic influence of the operator, the microphone/preamplifier assembly can be
detached from the main unit and connected via an extension cable.
Figure 4.5 – Microphone and pre-amplifier detached from the body of the SLM by use of an extension
cable. Rion NA 27.
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Other amplification
From the pre-amplification, the signal can undergo other amplification processes based on
what the signal is going to be used for such as RMS or frequency analysis.
Insert more information form the manual
Frequency weighting
You learnt in earlier modules that the human ear ‘hears’ sound differently to the absolute
sound pressure the ear receives. If the noise meter was not adjusted to accommodate for
this difference, it would be hard to relate the measured value to the effect on hearing or
amenity, and as such, the signal undergo a small transformation so that it represents human
hearing more accurately. This transformation is referred to as weighting.
The weighting is conducted early in the signals lifetime, and is simply an ‘arithmetic’
adjustment based on the frequency (via a circuit). The weightings are determined by the
international standard, which are shown in the table below;
This table can be graphed to show the observable effect on the flat signal received by the
microphone, as shown in the figure below;
Figure 4.6 – Graph showing the effect of weighting networks on noise signal.
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Analogue to digital conversion
The transduction of the sound pressure wave to the electrical signal at the microphone is
referred to as an analogue process. Analogue basically means ‘a continuous signal’, which is
great, but provides way too much information (because it is continuous).
Unfortunately, the rest of the instrument is a computer, which means that it operates as a
digital process and requires 0’s and 1’s to work with. Ultimately this means that the
continuous analogue signal needs to be chopped up or sampled and used in discrete
packages of information for further processing.
An analogue-to-digital converter (abbreviated ADC, A/D or A to D) is a device that converts
a continuous physical quantity (usually voltage) to a digital number that represents the
quantity's amplitude. The result is a sequence of digital values that have converted a
continuous-time and continuous-amplitude analogue signal to a discrete-time and discreteamplitude digital signal. This concept is represented in the figure below;
Figure 4.6 – Electrical symbol for ADC. http://en.wikipedia.org/wiki/Analog-to-digital_converter
Digital signal processing
Now that we have the signal in the digital form, we can use this to work with the data and
produce an enormous amount of information that wasn’t previously (or conveniently)
available to us by using the analogue signal alone.
Root Mean Square (RMS) circuit
How many averages are there? Most students state 'three, the mode, the mean and the
median", and they would be correct, if applied to the theory of central tendency. In terms of
averages, there are in fact many more than three - theoretically, you could even invent your
own - but we shall mention four, so we can highlight one in particular;
◗ Arithmetic mean
◗ Harmonic mean
◗ Geometric mean
◗ Root Mean Square (rms)
The RMS is how the sound level meter derives the value you see on the screen. Remember
that the measured value is called the LAeq, the ‘L’ means level, the ‘A’ is the weighting and
the ‘eq’ refers to equivalent. The RMS calculates the equivalent (RMS average) sound
pressure level over a specified time frame (which will be slow, fast or impulsive).
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The sound pressure level meter uses RMS detection to determine the continuous equivalent
sound pressure. The particular steps involved in evaluating the RMS signal are simple;
◗ The voltage, E, which changes over time is raised to the power of 2,
◗ Integration of the signal for the time interval T is performed.
◗ The result is divided by T
◗ The square root is extracted.
Just for kicks, the following figure attempts to illustrate the different types of average on a
data set of noise signals (decibel versus time). The rms will always be the highest value and
is equivalent to the AC/DC conversion factor of 0.707 (i.e. DC is ~70 % of the maximum AC
signal).
Figure 4.7 – Example of different average showing the rms. From the Nosie theory spreadsheet.
Time weightings and constant
During sound pressure level measurements, the level often fluctuates drastically, which
would make it difficult to evaluate readings if some kind of averaging is not applied. Sound
pressure level meters therefore provide the capability for index weighting (index averaging)
using the RMS circuit. The parameters of this weighting process are called the dynamic
characteristics and are determined by the time weighting.
Sound pressure level meters usually have a "Fast" and "Slow" setting for the time weighting.
The time range that is considered for averaging is narrow in the "Fast" setting and wide in
the "Slow" setting. In the "Fast" setting, the instantaneous level has a larger bearing on the
displayed value than in the "Slow" setting. From the point of view of the measurement
objective, the "Fast" setting is more suitable to situations with swiftly changing sound
pressure level, whereas the "Slow" setting yields a more broadly averaged picture.
The "Fast" setting is more commonly used, and sound pressure level or sound pressure level
values given without other indication are usually made with "Fast" characteristics.
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The "Slow" time weighting setting is suitable for measuring the average of noise with fairly
constant levels. Aircraft noise and high-speed train noise is usually transient noise with high
fluctuation, but here the "Slow" setting is used to determine the maximum level for each
noise event.
The "10 ms" setting of the NA-27 results in a very short time weighting, enabling the meter
to closely follow noise fluctuations.
The "Imp (Impulse)" setting enables the meter to track noise bursts of very short duration.
In the "Peak (Peak Hold)" condition, no averaging is carried out, and the peak value of the
frequency-weighted sound pressure waveform is displayed.
Frequency analysis
In order to be able to correctly weight sounds to the perception levels of the human ear, or
to get more detailed information about complex sounds it is necessary to divided the
frequency range of audible sound (20 – 20,000Hz) up into bands. This is done by using
electronic filters that reject all sound with frequencies outside the selected band. These
bands normally have widths of 1/3 of an octave or 1 octave.
For those not familiar with music an octave is a doubling of frequency (i.e. going from 260 to
520Hz is one octave). On a piano this means moving up eight white keys (hence the term
octave). On a sound frequency graph it means a frequency band where the higher frequency
is twice the lower frequency.
The spectrum analyser is the most commonly used analyser and offers the best features of
parallel and swept filter analysers. Modern dynamic signal analysers rapidly sample the
input signal, digitize the samples and store them in memory. The sampling rate, which is
generally 2.5 times the upper frequency limit of the analyser, sets the upper analysis limit.
The time record is converted to the frequency domain using the Digital Fast Fourier
transform (DFFT) algorithm. Analysers generally use either 1024 or 2048 sample points in
the time domain to give a 400-line or 800-line spectrum in the frequency domain.
Within the range of the analyser, the upper bound of the frequency analysis may be
selected, but the lower the upper frequency selected, the longer will be the required time to
acquire the 1024 (or 2048) samples. Each record of 1024 (or 2048) samples is processed
while the next record is being acquired.
In sound measurement, the values stated for frequency bands are normally centre
frequencies. This means that a range of sounds is allowed through the sound filter with the
frequency stated being the centre. An example of this is the 1000Hz centre frequency. In
this band a filter allows all sound of frequencies between 707 – 1414Hz through, but rejects
all others.
This process of dividing complex sound up into bands is called frequency analysis, and the
results of a frequency analysis are presented on a chart called a spectrogram or a frequency
histogram. Figure 4.10 shows the spectrogram of a complex waveform.
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Figure 4.10 – Spectrogram of a complex waveform. Brüel and Kjær.
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Measurement modes & functions
It is important to realise that the type of noise measurement made depends on the purpose
of the measurement. For example narrow frequency band determinations may be required
to identify the noise from a particular machine in a factory, or maybe only the dB(A) level is
required to find out whether the factory noise level exceeds the allowable levels according
the legislation. In the former case the machine may put out noise in a particular frequency
band, and narrow band frequency analysis would allow estimation of its contribution to
total noise only. In the latter case only the total noise in the area would be determined, and
no specific noise sources examined.
The type of noise source will also determine the type of noise measurement made. For
example steady noise sources require different types of measurement to impulsive noise
sources. The appropriate types of measurement for different types of noise sources are
summarised in the table below.
Modes of measurement
The sound pressure level (Lp, Leq or LE)
Statistical analysers also allow measurement of cumulative noise doses over time. Where
noise levels fluctuate in an unpredictable fashion over time, they are best represented by
the equivalent noise level which has the same acoustic energy (or noise dose) as the original
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fluctuating levels for the same period of time T. All measurements of this type are Aweighted, and so are sometimes represented by the symbol LAeq,T. Here the “A” represents
an A-weighting, the “eq” tells us that it is an equivalent noise or sound level, and the T is the
time is it averaged over. A single LAeq,T value can for example be used to represent the
fluctuating noise levels from an industrial workshop, which can then be compared with the
85dB(A) standard. This indicates whether there is a danger of exceeding the allowable
Australian 100% noise dose for an 8 hour day of 85dB(A) LAeq,8hr if the noise fluctuations
continue. Noise doses over 10 hours L10hr, and 18 hours L18hr are also commonly determined.
SPL weightings (A, C or Flat)
These are as explained above on page 9.
Sound Exposure Level (SEL, LE)
The levels of many sounds change from moment to moment. This variation must also be
accounted for when measuring noise levels. High quality sound integrating level meters
have a setting that allows for this – a measure referred to as the sound exposure level or
SEL. It is also given other symbols such as (LS) or (LEA,T). The sound exposure level is defined
as that level which lasting for 1 second has the same acoustic energy as a given noise
equivalent lasting for time T – hence the term (LEA,T).
Max, Min and Peak
Lmax is the maximum sound pressure level and Lmin the minimum sound pressure level
encountered during a measurement. In the NA-27, the sampling interval for A/D conversion
is 10 ms (100 samples per second), and the Lmax and Lmin values since the start of the
measurement are stored. Therefore the Lmax and Lmin readings up to the current point can
be displayed already during measurement.
The term peak refers to the measurement mode of Lpeak and is the waveform peak sound
pressure level for a given measurement interval that can be measured.
Percentile measurements, Lx
These are instruments that measure the distribution of fluctuating noise with time for the
purpose of assessing community noise and its potential to cause hearing damage. In
addition to providing energy averaged noise levels (such as Leq and LAeq) they also provide
information on how often certain sound levels are exceeded. For example they provide
values such as L1, L10, L50 and L90, which are the sound pressure levels exceeded 1%,10%,
50% and 90% of the time respectively. When these are used with A weightings these values
become LA10, LA50 and LA90 values which are commonly used by the NSW EPA for
investigating sound levels.
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Day-Night Sound Level (LDN)
The Day-Night Sound Level is the A-weighted equivalent sound level for a 24-hour period
with an additional 10dB weighting imposed on the equivalent sound levels occurring during
night time hours (10pm to 7am). Hence, an environment that has a measured daytime
equivalent sound level of 60 dB and a measured night time equivalent sound level of 50 dB,
can be said to have a weighted night-time sound level of 60 dB (50 + 10) and an LDN of 60 dB.
Operational functions
These include items such as memory functions. Each meter purchased will have a different
level of functionality in regards to its operational performance.
Operational consideration
Background noise
When measuring a certain sound in a certain location, all other sounds present at that
location except the measurement target sound are background noise (also called ambient
noise or dark noise). Since the sound pressure level meter will display the combination of
target sound and background noise, the amount of background noise must be taken into
consideration when determining the level of the target sound.
If the difference between the meter reading in absence of the target sound and the reading
with the target sound is more than 10 dB, the influence of background noise is small and
may be disregarded. If the difference is less than 10 dB, the values shown in the table below
may be used for compensation, to estimate the level of the target sound.
If for example the measured sound pressure level when operating a machine is 70 dB, and
the background sound pressure level when the machine is not operating is 63 dB, the
compensation value for the difference of 7 dB is -1 dB. Therefore the sound pressure level of
the machine can be taken to be 70 dB + (-1 dB) = 69 dB.
The above principle for compensating the influence of the background noise assumes that
both the background noise and the target sound are approximately constant. If the
background noise fluctuates, and especially if it is close in level to the target sound,
compensation is difficult and will often be meaningless.
Environmental
Noise meters are precision instruments and as such must be protected from shocks and
vibrations. Take special care not to touch the microphone diaphragm. The diaphragm is a
very thin metal film which can easily be damaged.
Common ambient conditions for operation of noise meters are as follows;
◗ temperature range -10 to +50ºC,
◗ relative humidity 30 to 90%.
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Protect the unit from;
◗ water,
◗ dust,
◗ extreme temperatures,
◗ humidity, and,
◗ direct sunlight
◗ air with high salt or sulphur content, gases, and stored chemicals.
Calibration
Factory electronic calibration
Factory calibrations are designed to check an instrument over its entire frequency range.
This is very time consuming, and the procedure involves specialized staff and equipment
dedicated to that purpose. As the term implies, the calibration is performed at a NATA
accredited laboratory, and most standards require recalibration every two years for the data
gathered by the noise meter to be legal.
Electrical calibration
Calibration of the meter can be performed electronically in a similar fashion to the factory
calibration but over a shorter range or using a single calibration point. It is performed by
using a externally or internally generated electrical signal of known amplitude and
frequency which is run into the microphone amplifier circuit, and checked against known
reference values and any deviation from the reference can be corrected by adjustment of a
preset control on the meter.
Although this calibration can check the amplifier, and the weighting networks and filters,
the microphone sensitivity is not checked. Thus, it is important to supplement this form of
calibration with regular acoustic calibration
Acoustic calibration
A tonal acoustic signal of known sound pressure level is applied to the microphone and the
meter reading is compared with the reference level. Any error outside the quoted calibrator
tolerance may be adjusted by the preset gain control (if available). Modern devices use 1000
Hz as the calibration frequency (at 94dB), as the same result is obtained with the Aweighting network switched in or out. Calibrators operating at other frequencies require all
weighting networks to be switched out during the calibration process.
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Figure 4.9 – Example of a pistonphone used for acoustic calibration of noise meters in the field.
The noise generating device is called a pistonphone and care should be taken to ensure that
there is a good seal between the microphone housing and calibrator cavity.
During calibration, the sensitivity adjustment on the sound level meter is adjusted to make
it read whatever the value equal to the sound pressure level generated by the pistonphone
calibrator. Calibration is accurate to ±0.5 dB for most instruments intended for use in the
field (general purpose sound level meters) and ±0.2 dB for precision instruments for
laboratory use. Large errors may indicate damage to either the sound level meter or the
calibrator, and in such cases both should be returned to the manufacturer for checking.
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Assessment task
After reading the theory above, answer the questions below. Note that;

Marks are allocated to each question.

Keep answers to short paragraphs only, no essays.

Make sure you have access to the references (last page)

If a question is not referenced, use the supplied notes for answers
Answer the following questions
1. List, and briefly describe, the difference between the four types of noise meter. 4mk
Type your answer here
Leave blank for assessor feedback
2. Which standard dines the electrical aspects of noise meters? 1 mk
Type your answer here
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3. Identify the standards associated with WHS and environmental monitoring. 2 mk
Type your answer here
Leave blank for assessor feedback
4. What are the three categories/class/type of instrument? What is the primary difference
between them? 3 mk
Type your answer here
Leave blank for assessor feedback
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Course Notes for delivery of MSS11 Sustainability Training Package
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Noise monitoring & evaluation
Study Module 4
5. What is an IASLM? 1 mk
Type your answer here
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6. What do the term integrating and averaging mean in relation to an IASLM? 2 mk
Type your answer here
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7. What does the microphone do? 1 mk
Type your answer here
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8. Which type of microphone is commonly used in Class 1 noise meters? 1 mk
Type your answer here
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9. Identify the three key operational characteristics of a condenser microphone. 3 mk
Type your answer here
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10. What does the process of amplification do to a signal? 2 mk
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Course Notes for delivery of MSS11 Sustainability Training Package
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Noise monitoring & evaluation
Study Module 4
Type your answer here
Leave blank for assessor feedback
11. What is the meant by the term frequency weighting? 2 mk
Type your answer here
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12. What is the difference between A, C and flat weightings? 3 mk
Type your answer here
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13. What is meant by the term RMS? How does it relate to the noise signal and the
measurement of LAeq? 6 mk
Type your answer here
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14. Identify the four common time constants. How does a slow setting differ from a fast
setting in terms of what is averaged? 4 mk
Type your answer here
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15. Briefly describe the term frequency analysis. 4 mk
Type your answer here
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Course Notes for delivery of MSS11 Sustainability Training Package
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Noise monitoring & evaluation
Study Module 4
Leave blank for assessor feedback
16. Explain the meaning of the term impulsive sound, and give one example. Why are
impulsive sounds potentially more damaging to human hearing than normal sounds? 4
mk
Type your answer here
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17. Explain the meaning of the following terms with respect to sound/noise level
measurement LA10, LA50 and LA90. 6 mk
Type your answer here
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18. Explain the difference between an equivalent sound level, a day night sound level and an
A-weighted sound exposure level. 6 mk
Type your answer here
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19. Why is correcting for background level so important? 2 mk
Type your answer here
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20. How is the background correction achieved? 2 mk
Type your answer here
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Course Notes for delivery of MSS11 Sustainability Training Package
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Noise monitoring & evaluation
Study Module 4
Leave blank for assessor feedback
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Study Module 4
Assessment & submission rules
Answers
◗ Attempt all questions and tasks
◗ Write answers in the text-fields provided
Submission
◗ Use the documents ‘Save As…’ function to save the document to your computer using
the file name format of;
name-classcode-assessmentname
Note that class code and assessment code are on Page 1 of this document.
◗ email the document back to your teacher
Penalties
◗ If this assessment task is received greater than seven (7) days after the due date (located
on the cover page), it may not be considered for marking without justification.
Results
◗ Your submitted work will be returned to you within 3 weeks of submission by email fully
graded with feedback.
◗ You have the right to appeal your results within 3 weeks of receipt of the marked work.
Problems?
If you are having study related or technical problems with this document, make sure you
contact your assessor at the earliest convenience to get the problem resolved. The name of
your assessor is located on Page 1, and the contact details can be found at;
www.cffet.net/env/contacts
Resources & references
References
(NSW), E. P. (2000). NSW Industrial Noise Policy. Sydney: Environmental Protection Authority (NSW).
(NSW), R. &. (2001). Environmental Noise Management Manual. Sydney: Roads & Traffic Authority
(NSW).
Australia, S. (1997). AS 1055.1-3. Homebush: Standards Australia.
Australia, S. (2005). OCcupational Noise Management, Part 1: Measurement and Assessment of
Noise Immission and Exposure. Homebush: Standards Australia.
Australia, S. (2011). Methods for the sampling & analysis of ambient air: Part 14: Meteorological
monitoring for ambient air quality monitoring applications. Homebush: Standards Australia.
Bies, D. &. (2003). Engineering Noise Control, 3rd Ed. London: Spon Press.
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Kester, W. (2004). Analogue-Digital Conversion. United States: Analogue Devices.
Maltby. (2005). Occupational Audiometry: Monitoring & protecting hearing at work. London:
Elselvier.
NOHSC. (2000). National Standard for Occupational Noise [NOHSC: 1007(2000), 2nd Ed. Canberra:
Australian Government.
Organisation, W. H. (1995). Occupational Exposure to noise: Evaluation, prevention & control.
Geneva: WHO Publishing.
Rossing, T. (2007). Handbook of Acoustics. New York: Springer.
South, T. (2004). Managin Noise & Vibration at Work. London: Elselvier.
Workcover, N. (2004). Code of Practice: Noise Management & Protection of Hearing at Work.
Sydney: Workcover NSW.
Workplace Health and Safety Regulation 2011. (n.d.).
Further reading and online aids
Nil
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