This document discusses noise pollution, including its definition, sources, measurement, effects on the environment and humans, monitoring devices, and methods for control and prevention. It defines noise pollution as unwanted sound that penetrates the environment from an external source. Major sources listed include street traffic, railroads, airplanes, and construction. Measurement units and health impacts are also summarized, along with legislative guidelines and strategies for noise control, including reducing noise at the source, blocking transmission paths, and using protective equipment.

1. NNooiissee PPoolllluuttiioonn
Ms Noor Rosyidah Binti Sajuni
School of Engineering
rosyidah@ucsi.edu.my

2. 2
Content
• Definition,
• sources of noise pollution,
• unit measurement,
• effects of noise pollution to environment and human,
• major noise monitoring devices,
• control and preventive action.

3. 3
Definition
• Sound:
Sound, a manifestation of vibration, travels in wave patterns through
solids, liquids and gases. The waves, caused by vibration of the molecules,
follow sine functions, typified by the amplitude and wavelength (or
frequency)
Sound waves of equal amplitude with increasing frequency from top to
bottom
• Noise Pollution:
Any unwanted sound that penetrates the environment is noise pollution.
In general noise pollution refers to any noise irritating to one's ear which
comes from an external source.

4. 4
Sound propagation

5. 5
Level and the Decibel
• Unit measurement: Decibel (dB, or tenth (deci) of a Bel)). The decibel is named after Alexander
Graham Bell, the Canadian pioneer of the telephone who took great personal interest in the
problems of deaf people.

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Power / Intensity / Pressure
Intensity & pressure – measured using
instruments
Power is calculated
Power is basic measure of acoustic
energy it can produce
& is independent of surroundings

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Power / Intensity / Pressure ???
Sound Pressure:
evaluation of harmfulness and
annoyance of noise sources
Sound Intensity:
location & rating of noise sources
rate of energy flow per unit area
I=P2/ρc
Sound Power:
for noise rating of machines
unique descriptor of noisiness of
source
W=4πr2I

8. 8
Sound power and intensity

9. 9
Sound pressure level

10. 10
Effect of multiple sound sources
• Average Sound power
æ N Lpn
ö
å
= 10log ç 10
10
10
¸
è =
1
ø
Lp
tot
n
• Average Sound pressure
N Li
20log 1 1020
= å
p N
L
1
• Equivalent continuous equal energy level
10log (10 )( )
1
10
i
N Li
eq L = å t

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How sound is measured
•Pressure, P, usually Pascals
•Frequency, f, usually Hertz
•Intensity, I, usually W/m2
•Bels, L’, derived from logarithmic ratio
•Decibels, L, derived from bels
P = 1/f
I = W/A
L’ = log (Q/Qo)
L = 10*log (Q/Qo)

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- TThhee ffoolllloowwiinngg pphhoottooss sshhooww ttwwoo ddiiffffeerreenntt
kkiinnddss ooff ddeecciibbeell mmeetteerrss::

13. 13
Sources of noise pollution
• Street traffic
• Rail roads
• Airplanes
• Constructions
• Consumer products

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Sound and human hearing – Frequency
Humans are less sensitive to low frequency sound and more sensitive to high
frequency sound. Therefore, sometimes the dB scale is adjusted to take this
into account:
A-weighting (db(A)): adjusts overall scale so it better matches what the
human ear would hear
C-weighting (dB(C)): adjusts scale for loud or low frequency sounds
B-weighting (dB(B)): adjusts by factors that are “in between” the A-weighted
factors and C-weighted factors (rarely used)

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Effect of Noise Pollution
• There are about 25000 hair cells in our ear which create wave in our ear,
responding to different levels of frequencies.
• With increasing levels of sound the cells get destroyed decreasing our ability to
hear the high frequency sound.
• Constant exposure to loud noise → temporary / permanent hearing loss depending
on:
– volume
– Duration
– Repetition of exposure
• Irreversible hearing loss.
• Blood pressure rise of 5 to 10 mmHg on 8 hrs of exposure to even 70 dV of sound
level.
• Hearing loss begins at 80- 90 dBA. 140 dbA is painful and 180 dB can even kill a
person.
• Most of the electronic vehicles and motors are above 80 dB level.
• High noise levels may interfere with the natural cycles of animals, including
feeding behavior, breeding rituals and migration paths.

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Impact of Noise
• Annoyance:
– It creates annoyance to the receptors due to sound level fluctuations.
The periodic sound due to its irregular occurrences causes displeasure
to hearing and causes annoyance.
• Physiological effects:
– The physiological features like breathing amplitude, blood pressure,
heart-beat rate, pulse rate, blood cholesterol are effected.
• Loss of hearing:
– Long exposure to high sound levels cause loss of hearing. This is
mostly unnoticed, but has an adverse impact on hearing function.
• Human performance:
– The working performance of workers/human will be affected as they'll
be losing their concentration.

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Impact of Noise (continue)
• Nervous system:
– It causes pain, ringing in the ears, feeling of tiredness, thereby
effecting the functioning of human system.
• Sleeplessness:
– It affects the sleeping there by inducing the people to become restless
and loose concentration and presence of mind during their activities
• Damage to material :
– The buildings and materials may get damaged by exposure to
infrasonic / ultrasonic waves and even get collapsed.

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Symptoms of occupational hearing loss
• Feeling of fullness in the ear.
• Sounds may seem muffled.
• Cannot hear high frequency sounds.
• Ringing in the ears while listening to the high frequency sounds.
• Loud noise for a long period of time, or sudden burst of sound can cause
occupational hearing loss.
• Hearing that does not return after an acute noise injury is called a
permanent threshold shift.

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Legislation/Regulatory guidelines
• Factories And
Machinery (Noise
Exposure) Regulations
1989

20. 20
Guidelines for Environmental Noise Limits
and Control, DOE

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Noise Management Strategy

24. 24
Noise Control Plan
i. design stage - design out or minimise noisy work;
ii. organizational stage - plan how the site will be managed and the risks
controlled;
iii. contractual stage - ensure that contractors meet their legal requirements;
and
iv. building phase - assess the risks, eliminate or control them, and review
the assessment.
Before work starts on site:
i. implement a low-noise procurement policy (purchase and hire) for
machinery and work equipment;
ii. set desired noise-control requirements in the tender specifications;
iii. plan the work process to minimize worker exposure to noise; and
iv. implement a noise-control programme (for example, by planning,
training, induction, site layout, maintenance activities).

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Noise Control at Source
• Reducing the noise levels from domestic sectors:
– The domestic noise coming from radio, tape recorders, television sets, mixers,
washing machines, cooking operations can be minimized by their selective and
judicious operation. By usage of carpets or any absorbing material, the noise
generated from felling of items in house can be minimized.
• Maintenance of automobiles:
– Regular servicing and tuning of vehicles will reduce the noise levels. Fixing of
silencers to automobiles, two wheelers etc., will reduce the noise levels.
• Control over vibrations:
– The vibrations of materials may be controlled using proper foundations, rubber
padding etc. to reduce the noise levels caused by vibrations.
• Low voice speaking:
– Speaking at low voices enough for communication reduces the excess noise
levels.
• Prohibition on usage of loud speakers:
– By not permitting the usage of loudspeakers in the habitant zones except for
important meetings / functions. Now-a-days, the urban Administration of the
metro cities in India, is becoming stringent on usage of loudspeakers.

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• Selection of machinery:
– Optimum selection of machinery tools or equipment reduces excess noise
levels. For example selection of chairs, or selection of certain
machinery/equipment which generate less noise (Sound) due to its superior
technology etc. is also an important factor in noise minimization strategy.
• Maintenance of machines:
– Proper lubrication and maintenance of machines, vehicles etc. will reduce noise
levels. For example, it is a common experience that, many parts of a vehicle
will become loose while on a rugged path of journey. If these loose parts are not
properly fitted, they will generate noise and cause annoyance to the
driver/passenger. Similarly is the case of machines. Proper handling and
regular maintenance is essential not only for noise control but also to improve
the life of machine.

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Control in the transmission path
• Installation of barriers:
– Installation of barriers between noise source and receiver can attenuate
the noise levels. For a barrier to be effective, its lateral width should
extend beyond the line-of-sight at least as much as the height (See Fig.
5).
– The barrier may be either close to the source or receiver, subject to the
condition that, R <<D or in other words, to increase the traverse length
for the sound wave. It should also be noted that, the presence of the
barrier itself can reflect sound back towards the source.
– At very large distances, the barrier becomes less effective because of
the possibility of refractive atmospheric effects. Another method, based
on the length of traverse path of the sound wave is given at Fig. 6.

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29. 29

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• Design of building:
– The design of the building incorporating the use of suitable noise
absorbing material for wall/door/window/ceiling will reduce the noise
levels.
– The approximate reduction of outside noise levels using typical
exterior wall construction is given at Table 6. The reduction in noise
levels for various frequencies and the A-weighted scale are shown.
– Variations in spectrum shape may change this A-weighted value by as
much as +/- 3 dB.

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• Installation of panels or enclosures:
– A sound source may be enclosed within a paneled structure such as room as a
means of reducing the noise levels at the receiver.
– The actual difference between the sound pressure levels inside and outside an
enclosure depends not only on the transmission loss of the enclosure panels but
also on the acoustic absorption within the enclosure and the details of the panel
penetrations which may include windows or doors.
– The product of frequency of interest and surface weight of the absorbing
material is the key parameter in noise reduction through transmission loss.
– With conventional construction practices, the high-frequency transmission loss
of a panel becomes limited to around 40 dB, owing to the transmission of
sound through flanking paths other than the panel itself.
– Examples of such flanking are structural connections or ducts joining the two
spaces on either side of the panel of interest. Procedures for detailed design
examples.

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• · Green belt development:
– Green belt development can attenuate the sound levels. The degree of
attenuation varies with species of greenbelt.
– The statutory regulations direct the industry to develop greenbelt four
times the built-up area for attenuation of various atmospheric
pollutants, including noise.

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• Using protection equipment
– Before employing the use of protective equipment, the various steps
involved in the noise management strategy are illustrated.
– Protective equipment usage is the ultimate step in noise control
technology, i.e. after noise reduction at source and/or after the
diversion or engineered control of transmission path of noise.
– The first step in the technique of using protective equipment is to
gauge the intensity of the problem, identification of the sufferer and his
exposure to the noise levels.
– For the Regulatory standards pertaining to time of exposure vs.
maximum noise levels permitted in a workspace environment.

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• The usage of protective equipment and the worker's exposure to the high noise
levels can be minimized by -
– Job rotation: By rotating the job between the workers working at a
particular noise source or isolating a person, the adverse impacts can be
reduced.
– Exposure reduction: Regulations prescribe that, noise level of 90 dB (A)
for more than 8 hr continuous exposure is prohibited. Persons who are
working under such conditions will be exposed to occupational health
hazards. The schedule of the workers should be planned in such a way that,
they should not be over exposed to the high noise levels.
– Hearing protection: Equipment like earmuffs, ear plugs etc. are the
commonly used devices for hearing protection. Attenuation provided by
ear-muffs vary widely in respect to their size, shape, seal material etc.
Literature survey shows that, an average noise attenuation up to 32 dB can
be achieved using earmuffs .