Environmental Monitoring
& Technology Series
Noise monitoring &
evaluation
For Technicians
Study module 1
Introduction
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Noise monitoring & evaluation
Study Module 1
Assessment details
Purpose
This subject covers the ability to site and set up basic ‘ground level’ meteorological
equipment and collect and record reliable data. It also includes the ability to assess data
quality, interpret significant data features and use the data to ensure the validity of air and
noise monitoring measurements.
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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◗ I have read and understood the SAG for this subject/unit…
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◗ I know the due date for this assessment task…
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Details
Student name
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Assessor
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Class code
NME
Assessment name
SM1
Due Date
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Total Marks Available
30
Marks Gained
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Final Mark (%)
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Marker’s Initials
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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
Unless you’re unfortunate enough to be deaf, sound is such a common part of everyday life
that we rarely appreciate all of its functions. It provides us with pleasure - such as that
obtained by listening to music or the gentle sounds of a rain forest. It allows us to
communicate with other human beings and animals. It can be used to alert or warn us - for
example a ringing telephone means that someone wished to talk to us, or a wailing siren
signifies danger.
Sound being one of our principle senses also permits us to make quality evaluations and
diagnoses. We can hear when our car engine misfires telling us it needs tuning, a squeaking
valve on an instrument means it needs lubrication; a heart murmur tells us we are sick; and
so on.
Not all sounds are associated with pleasure. Many of the sounds associated with our
modern society annoy us. This is of course a subjective judgement. For example some
people enjoy “heavy metal music”, whilst others think that its only function is to kill the
neighbours grass if it is played loud enough. Any sound that is unpleasant or unwanted is
called noise.
The level of annoyance of noise depends not only on the quality of the sound, but also our
attitude towards it. The sound of a jet aircraft taking off may be pleasant to the ears of the
pilot and passengers, but will be ear-splitting agony for the people living near the end of the
runway. Sound doesn't need to be loud to annoy. A rattling window on a quiet night, or a
dripping tap can be just as annoying as a jet aircraft. The Chinese water torture used
repetitive quiet sounds from a dripping tap.
Loud sounds can damage and destroy. A sonic boom can shatter windows and shake plaster
off walls. But the most unfortunate case is when sound damages the delicate mechanism
designed to receive it the human ear. When this happens our hearing is impaired. The loss
may be temporary, or permanent depending on how often and for how long we are
exposed.
The difference between sound & noise
When an object moves backward and forward in a repetitive motion it is said to vibrate or
oscillate. If this occurs in a medium such as air the particles near the object are affected and
start vibrating at the same rate, producing variations in the normal air pressure. This
disturbance spreads, and eventually may reach a human ear, which translates these
vibrations into a sensation that we call sound.
The simplest definition of sound is therefore any pressure variation or oscillation in a
conductive medium that may be detected by the human ear. The most common conductive
media are air or water, although sound may be conducted directly through solid structures
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Study Module 1
such as metal pipes etc. This definition does not include any oscillation that cannot be
detected by the human ear.
An example of this would be fluctuations in air pressure caused by weather changes. These
can be accurately measured by a barometer, but are too slow to be picked up by a normal
human ear, with the exception of when we move rapidly from one height to another, such
as in an aircraft. In this instance we do not hear sound but rather experience a slow pressure
build up in the ear.
Figure 1.1 – Example of a sound pressure wave with inferences of sounds and noise. Source
unknown
Noise is characterised by a lack of order or regularity in its sound wave. This generally (but
not always) results in tones that are less pleasing to the human ear. Musical instruments by
contrast produce regular patterns in the waveforms that they generate.
A reasonable definition of noise is therefore a complex sound that lacks regularity or order
in its waveform. It may also be defined more simply as any unwanted or undesired sound, or
even as any sound not native to the environment although this last definition would make
all musical instruments noise – a view with which many would not concur.
What this unit will teach you
By the end of this unit, you will know enough knowledge and have enough skill to engage in
the practice of occupational (workplace) and environmental noise monitoring for the
purposes of both;
◗
compliance based monitoring (e.g. licenses & OHS) and
◗
environmental impact assessments
The next step is applying what you know in the workplace.
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Outside of specific legislative requirements, the need for noise evaluation has two major
stems;
◗ Protection of hearing
◗ Protection of amenity (or from annoyance)
Protection of hearing
First of all, let there be a distinction between hearing and listening. Hearing is the
transduction of sound pressure into perceived sound (or mechanical energy into electrical
energy), which is done via the ears. Listening is hearing with interpretation of what is heard.
To understand what is in need of protection, we need to understand the basics of the
hearing process itself.
How we hear
The human ear is constructed of three main sections;
◗ the outer ear,
◗ the middle ear,
◗ and the inner ear.
The outer ear consists of a fleshy outer section called the Auricle or pinna and the auditory
canal, the hole in the side of our head through which the sound waves enter. The outer ear
is responsible for collecting the sound waves.
Figure 1.2 – The outer ear. From http://www.virtualmedicalcentre.com/anatomy/ear/29.
The middle ear, on the inner side of the eardrum, is responsible for conduction of sound
waves to the internal ear. This process is often referred to as modulation. It is a narrow
passage, extending vertically for about 15 mm and then about 10-15mm horizontally. There
is a special tube called the Eustachian tube which allows the middle ear direct
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communication with the back of the nose and throat. This allows air into and out of the
middle ear.
The middle ear also contains three small, movable bones the hammer (malleus), the anvil
(incus), or anvil; and the stapes, or stirrup, collectively called the ossicles. These connect the
eardrum acoustically to the fluid-filled internal ear.
Figure 1.3 – The middle ear. From www.medicalook.com
The inner ear is the part of the temporal bone containing the organs of hearing and balance.
It is directly connected to the filaments of the auditory nerve. It is separated from the
middle ear by the or oval window (fenestra ovalis).
The inner ear consists of membrane bound canals housed in the temporal bone and is
divided into the cochlea, the vestibule, and three semicircular canals. All these canals
communicate with one another and are filled with a gelatinous fluid called endolymph.
Figure 1.4 – The structure of the human ear. From learningthroughlistening.org
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The whole process is one of the best examples of how nature uses biology as an effective
transducer, in this case, transferring sound pressure into electrical signals. A summary of the
process is as follows;
1.
Soundwaves are created
2.
The sound wave is collected by the outer ear
3.
The wave travels down the ear canal
4.
The force of the wave is absorbed by the ear drum
5.
The ear drum vibrates
6.
The vibrations cause the three middle ear bones to vibrate
7.
The middle ear vibrations are transferred to the fluid filled cochlea
8.
The fluid vibrations cause the cilia to vibrate
9.
Movement of the cilia cause electrical impulses in the nerve endings of the cilia
10.
The nerve signals travel along the auditory nerve to the brain
11.
The brain processes these signals into the sounds we hear
The process of hearing
Sound waves are carried through the external auditory canal to the eardrum (also known as
the tympanic membrane), causing it to vibrate. These vibrations are transferred by the
hammer, anvil and stirrup in the middle ear through the oval window to the fluid in the
inner ear. This disturbs the fluid in the cochlea and stimulates the movement of thousands
of very sensitive fine hair-like projections called hair cells. Collectively these projections are
called the Corti.
The hair cells transmit vibrations directly to the auditory nerve, which changes them into
impulses, which carry information to the brain. The response of the hair cells to vibrations of
the cochlea provides information about sound in a way that is interpretable by the brain's
auditory centres.
The range of human hearing
The range of hearing, like that of vision, varies in different persons. When describing the
range of human hearing, we don’t use the volume or ‘loudness’ in decibels alone, but rather
the spectrum of the frequency (reciprocal of seconds per cycle (period), or c/s, commonly
called Hertz (Hz)), all of which is described in later chapters.
The maximum range of human hearing includes sound frequencies from about 16 – 28,000
Hz, but the average healthy person has a normal hearing range of about 20 – 16,000 Hz. This
may be extended to 20 – 20,000Hz in young people.
The least noticeable change in tone that can be picked up by the ear varies with pitch and
loudness. A change of vibration frequency (pitch) corresponding to about 0.03 per cent of
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the original frequency can be detected by the most sensitive human ears in the range
between 500 and 8,000Hz. The ear is less sensitive to frequency changes for sounds of low
frequency or low intensity.
The sensitivity of the ear to sound intensity (loudness) also varies with frequency. Sensitivity
to change in loudness is greatest between 1,000 to 3,000Hz, where a change of one decibel
can be detected—and becomes less when sound-intensity levels are lowered.
Figure 1.5 – Range of human hearing – dB vs Frequency. From http://sound.westhost.com.
What specifically is being protected?
The hair cells. Prolonged exposure to loud sounds can damage the hair cells, which may
result in hearing impairment. Initially damage may only occur to a few hair cells – which is
hardly noticeable as the brain can compensate for the loss, but as more are damaged it
cannot make up for the loss of information and noticeable changes in hearing occur.
Figure 1.6 – The hair cell and its movement response. From www.nlm.nih.gov.
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Most commonly speech and background cannot be distinguished, whilst some words may
mix together. By the time this begins to occur it is likely that irreparable damage to the ear
has occurred. Hearing loss due to noise exposure is generally greatest at those frequencies
where the human ear is most sensitive – around 4000Hz.
Protection against loss of amenity
Another reason that noise monitoring occurs is due to loss of amenity, which refers to any
feature of the community or residence that provides comfort, convenience, or pleasure,
where that pleasure is lost due to the ingress of noise.
Loss of amenity is the most difficult aspect of noise to measure, as it is purely subjective,
and as such requires significant resources (in terms of calculations, indices and ranking
systems) to be employed to generate a system of loss calculation that is both relevant and
fair to all stakeholders involved.
Figure 1.7 – Images depicting noisy environment (left) and noise creep (right). You should notice that
noise creep continuously rises and is difficult to detect the change over time. Source unknown.
Apart from obvious noise transgression by construction activities and the like, most loss of
amenity is a slowly occurring process and is referred to as noise creep. This adds to the
complexity of the analytical determinations. It is for this reason that this course, and
subsequently these notes do not delve heavily into this awkward area of noise assessment.
We’ll leave that to the experts.
Legislation, regulations, standards & codes of practice
Although law is not the most interesting subject, considering it is the sole reason for the job
description of environmental technician being in existence, its discussion is more than
warranted. What follows is a summary of the laws, regulations, standards and codes of
practice that were in place in each state and territory accurate to the time of writing.
Workplace & occupational laws
These laws are designed to protect workers hearing. To state the obvious, it only protects
workers, it does not protect community or individuals outside of the workplace. Although
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each state has specific legislation associated with the administration and execution of
workplace laws, there are federal laws that cover noise.
The result of this is that workplace noise dosage in Australia cannot exceed 85 dB over an 8
hour workday (or normalised equivalent if longer or shorter hours cover the workday, as
found in some shift work).
This topic is covered in significant detail in chapter 6, so we shall not spoil it here.
Environmental laws
Another area of law is environmental. These laws are less succinct than the OHS laws, and
may in fact be covered under many laws, depending upon the state or territory you are
working in. Furthermore, environmental noise control may fall under the jurisdiction of
many state government departments. Generally speaking though, the legislation all shares
similar aims, which are to minimise the effect of industrial/road/construction noise on the
community. This topic is the subject of chapter 7.
Miscellaneous laws & other standards
Community noise differs slightly from general environmental noise as it is municipal or
residentially focused and is monitored through the various state governments versions of
the Local Government Acts.
Further to this it can be subjectively (and objectively) measured by various law enforcement
officers such as the police. This aspect of noise is only briefly mentioned in these notes as
the two focuses are occupational and environmental.
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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
Complete the following table of terms and definitions. 7 mk
Term
Definition
Sound
Type your answer here
Noise
Type your answer here
Pressure
Type your answer here
Oscillation
Type your answer here
Outer ear
Type your answer here
Middle ear
Type your answer here
Inner ear
Type your answer here
Answer the following questions
a) List and define two aspects of our lives need protection from noise? 4 mk
Type your answer here
Leave blank for assessor feedback
b) Briefly describe how we hear. 5 mk
Type your answer here
Leave blank for assessor feedback
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c) Describe what is meant by the ‘range of human hearing’. State the numerical range. 3 mk
Type you answer here
Leave blank for assessor feedback
d) What specific part of the ear gets damaged by noise? Describe how it is damaged. 5 mk
Type your answer here
Leave blank for assessor feedback
e) What is meant by the term ‘amenity’? 2 mk
Type your answer here
Leave blank for assessor feedback
f) What is ‘noise creep’ and why is it bad? 4 mk
Type your answer here
Leave blank for assessor feedback
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Assessment & submission rules
Answers
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◗ Write answers in the text-fields provided
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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;
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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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