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Abdul Barey Shah
Noise Pollution
Sound is the main means of communication in many animals including humans. A low
sound is pleasant and harmless. A loud unpleasant sound or an unwanted sound of any
kind is called noise. The world noise is derived from the Latin ‘nausea’ meaning a feeling
of sickness at the stomach with an urge to vomit. Noise is defined as unwanted sound”,
“Sound without value” or “disagreeable sound” or wrong sound, in the wrong place at the
wrong time.”
Noise pollution is unwanted sound “decomposed into the environment without regard to
the adverse effect it may have (Odum).
Noise pollution may also be defined in a number of ways e.g.
Any unwanted electromagnetic signal that produces a jarring or displeasing effect and
which interferes with human communication comfort and health.
A persistent, often excessive and disturbing level of noise considered as a harmful factor
in a given environment, is called noise pollution.
The sound intensity is measured in decibel (dB), which is tenth part of the longest until
Bel, named after Alexander Graham Bell. One dB is equal to the faintest sound a human
ear can hear.
Sound beyond 80 dB harms hearing system and so it can be safely regarded as pollutant.
The largest noise a man can hear without much discomfort is thus about 80 dB .
The central pollution control Board committee has recommended permissible noise levels
for different locations as given in table 4.5:
Table 4.5 Noise standards recommended by C.P.C.B Committee:
Sources of Noise Pollution
The source of noise are varied and too many. Noise is either natural such as thunder or
manmade. The sources of manmade noise are more in urban and industrial areas than in rural
areas. The sources, in general may be stationary or mobile. For a better understanding of the
subject, the sources of noise can be classified in following categories:
(i) Transportation / Traffic Noise: It includes road traffic noise, aircraft noise and rail
traffic noise. With the increasing number of motor vehicles and trains inhabitants of cities are
generally subjected to a high level of transport noise which gradually deafens them, as
compared to those living in quieter towns. For example the din at the railway station in
Bombay often rises above 75dB and is considered comfortable for the human ear. But the
hooting of trains creates strain on ear because the noise level rises to 130dB, decreasing to
90dB at a distance of about 10 meters.
Aircraft noise is variable and intermittent, and is not continuous like the road traffic noise.
This source has been increasing during recent years especially close to international airports,
and has now become a serious problem. Cities around the world have banned or reduced
flights at night, and also prescribed noise limits.
Noise generated from highway traffic is one of the major sources of noise pollution. Highway
noises are of two types, viz, noises generated by individual vehicles and noises generated by
a continuous flow of vehicles of all types.
(i)
(ii)
Industrial Noise: In Industries, noise is the byproduct of energy conversion. The
major sources of noise in an industrial plant may include electromechanical
machines (like motors, generators etc) impact machines (like punching, stamping
hammers, etc) combustion processes (furnaces), fluid motion (compressors, fans
etc) and other mechanical parts (like shafts, gears etc). This is also called
occupational noise and workers in these industries are subjected to noise for about
8hours daily.
Neighborhood Noise: It has been defined as the variety of sources of noise which
may cause disturbance and annoyance to the general public. This type of noise
includes disturbances from household gadgets and community. Common noise
makers are musical instruments, TV, VCR, radio, transistors, telephones, washing
machines,vacuum cleaners, fans, mixers, coolers, air conditioners and loud
speakers etc.
It includes the noise generated during functions, festivals, religions activities (Like
Marriage ceremony, Diwali, and Holy etc).
Thus the variety of sources of noise may cause disturbance and annoyance to the public.
Effects of Noise Pollution: Noise affects human body in an number of ways, these may be
classified as auditory -effects and non- auditory effects.
(i) Auditory effects: Noise can damage the ear and cause temporary or permanent noise
induced hearing loss (NIHL) depending upon the intensity and duration of the sound level.
This is seen in those persons who are exposed to high noise levels over a long span for
example workers working in textile industries steel industries are exposed to more than 105
dB for eight hours per day and suffer from temporary or permanent noise induced hearing
loss.
If the ear receives a noise level of over 90 dB for more than few minutes then the auditory
sensitivity is reduced. This effect is called the temporary threshold shift (TTS). The most
commonly occurring ear damage is caused by continuous periods of high intensity noise as
found in some factories and other work situations. Under these conditions the
permanentthreshold shift (PTS) and progressive hearing deterioration results. Besides
progressive hearing loss, there may be instantaneous damage or acoustic trauma which may
be caused by very high intensity impulse type noise resulting from an explosion or sudden
excessive noise of over 150 dB.
(i)
a.
b.
c.
d.
e.
Non- Auditory effects: These are also alarming because of the fact that they may
also cause severe diseases. These effects include.
Speech Interference: A person faces problems in understanding another person
talking to him in an environment with high background noise level. Noise levels thus
affect the efficiency of schools, offices and other working places where
communication is of vital importance. External sounds can also interfere with
conversation and use of the telephone as well as the enjoyment of radio and TV.
Sleep interference: Noise causes interferences in sleep and it is a health hazard, since
it deprives a person of the restorative process for his organs to renew their supply of
energy and nutritive elements provided by a good night’s sleep. The loss of sleep
from noise affects personal well being and job performance. The preferable level is
below 40 dB.
Task interference: The effect of noise on the human performance of tasks is a
complicated subject that is under continued study. Many people complain that noise
makes them mentally ill and reduces their working efficiency. Noise actually reduces
the accuracy of work than to reduce the quantity of work.
Effects on Health and Behavior: One of the non- pathological or psychological
effect of noise is physical or mental fatigue and lack of concentration. In industrial
stations this effect results in lowered efficiency, reduced work rate and higher chances
for accidents. Noise also causes anxiety and stress reactions and in some cases fright.
Pathological and other effects: These effects are produced by particular noise
frequencies causing vibration or resonance in human bodies. High frequency sound
above, the normal audible range can affect the semi-circular canals of the inner and
make one suffer from nausea excessive fatigue headaches and vomiting. It has been
observed that there are increased incidences of birth defects, stillbirths, and unusually
low weight among children born to mother living near high noise producing sources
such as air ports, blast sites etc.
Control of Noise Pollution
According to a WHO report “of all environmental problems noise is the easiest to control”.
The efforts to control noise are usually aimed at lowering the sound intensity of the noise
source. The main methods to control noise are:
(i)
(ii)
(iii)
(iv)
(v)
(vi)
Noise producing industries, railway stations, aerodromes should be located away
from human settlements. This acoustic or proper zoning should be strictly
enforced.
Railways and main roads should be away from dwelling and working sites.
Noisy machines should be installed in sound- proof chambers.
Proper lubrication and maintenance of machines can reduce noise, quieter
machines should be produced to replace the noisy ones.
Protection to workers can be provided through wearing devices such as ear plugs
and muffs or cotton plugs which reduce the noise and protect the receiver.
Attempts can also be made to deflect the sound away from the receives e.g.
mechanically directing jet exhaust noise upward instead of directing it
downwards. This will reduce a jet plane sound to a great extent.
(vii)
Noise can be reduced by prescribing noise limits for vehicular traffic. Formation
of silent zones especially near hospitals, nursing homes, schools would be an
effective measure.
(viii) Planting of trees in many rows on both sides of roads and around residential areas
as well as industrial areas or industries.
(ix)
Suitable legislative measures should also be taken to project the public from noise
pollution and to punish offenders.
(x)
People should be educated through mass- media like TV, radio, news reels in
Cinema halls about the harmful effects of noise pollution will help in long way in
controlling noise pollution.