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Noise Pollution : |
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Noise
Pollution
Noise may not seem as harmful as the contamination of air or
water, but it is a pollution problem that affects human health
and can contribute to a general deterioration of environmental
quality.
Noise is undesirable and unwanted sound. Not all sound is noise.
What may be considered as music to one person may be noise to
another! It is not a substance that can accumulate in the environment
like most other pollutants. Sound is measured in a unit called
the 'decibel' (dB).
There are several sources of noise pollution that contribute
to both indoor and outdoor noise pollution. Noise emanating
from factories, vehicles, and playing of loudspeakers during
various festivals can contribute to outdoor noise pollution,
while loudly played radio or music systems, and other electronic
gadgets can contribute to indoor noise pollution. A study conducted
by researchers from the New Delhi-based National Physical Laboratory
show that noise generated by firecrackers (presently available
in the market) is much higher than the prescribed levels. The
permitted noise level is 125 decibels, as per the Environment
(Protection) (second amendment) Rules, 1999.
The differences between sound and noise is often subjective
and a matter of personal opinion. There are, however, some very
harmful effects caused by exposure to high sound levels. These
effects can range in severity from being extremely annoying
to being extremely painful and hazardous.
Decibel
levels of common sounds
dB |
|
Environmental
Condition |
0 |
|
Threshold of hearing |
10 |
|
Rustle of leaves |
20 |
|
Broadcasting studio |
30 |
|
Bedroom at night |
40 |
|
Library |
50 |
|
Quiet office |
60 |
|
Conversational speech (at 1m) |
70 |
|
Average radio |
74 |
|
Light traffic noise |
90 |
|
Subway train |
100 |
|
Symphony orchestra |
110 |
|
Rock band |
120 |
|
Aircraft takeoff |
146 |
|
Threshold of pain |
Effects of noise pollution on physical health
The most direct harmful effect of excessive noise is physical
damage to the ear and the temporary or permanent hearing loss
often called a 'temporary threshold shift' (TIS). People suffering
from this condition are unable to detect weak sounds. However,
hearing ability is usually recovered within a month of exposure.
In Maharashtra, people living in close vicinity of Ganesh mandals
that play blaring music for ten days of the Ganesh festival
are usually known to suffer from this phenomenon. Permanent
loss, usually called 'noise-induced permanent threshold shift'
(NIPTS) represents a loss of hearing ability from which there
is no recovery.
Below a sound level of 80 dB hearing loss does not occur at
all. However, temporary effects are noticed at sound levels
between 80 and 130 dB. About 50% of the people exposed to 95
dB sound levels at work will develop NIPTS and most people exposed
to more than 105 dB will experience permanent hearing loss to
some degree. A sound level of 150 dB or more can physically
rupture the human eardrum.
The degree of hearing loss depends on the duration as well as
the intensity of the noise. For example, 1 hour of exposure
to a 100 dB sound level can produce a TIS that may last for
about one day. However, in factories with noisy machinery, workers
are subjected to high sound l~vels for several hpurs a day.
Exposure to 95 dB for 8 hours everyday for over a period of
10 years may cause about 15 dB of NIPTS. In addition to hearing
losses, excessive sound levels can cause harmful effects on
the circulatory system by raising blood pressure and altering
pulse rates.
Effects of noise
pollution on mental health: Noise can also cause emotional
or psychological effects such as irritability, anxiety and stress.
Lack of concentration and mental fatigue are significant health
effects of noise. It has been observed that the performance
of school children is poor in comprehension tasks when schools
are situated in busy areas of a city and suffer from noise pollution.
As noise interferes with normal auditory communication, it may
mask auditory warning signals and hence increases the rate of
accidents especially in industries. It can also lead to lowered
worker efficiency and productivity and higher accident rates
on the job.
Thus, noise is just more than a mere nuisance or annoyance.
It definitely affects the quality of life. It is therefore important
to ensure the mitigation or control of noise pollution.
Permitted noise levels
Ambient
Noise Levels dB Zone |
|
Day-time |
|
Night-time |
Silent Zone |
|
50 |
|
40 |
Residential Zone |
|
55 |
|
45 |
Commercial Zone |
|
65 |
|
55 |
Industrial Zone |
|
70 |
|
70 |
A standard safe time limit has been set for exposure to various
noise levels. Beyond this 'safe' time continuing exposure over
a period of a year will lead to hearing loss.
Duration |
|
dB |
8 hours |
|
90 |
4 hours |
|
93 |
2 hours |
|
96 |
1 hours |
|
99 |
30 minutes |
|
102 |
15 minutes |
|
105 |
7 minutes |
|
108 |
4 minutes |
|
111 |
2 minutes |
|
114 |
1 minutes |
|
117 |
30 seconds |
|
120 |
Instantaneous rupture of membrane |
|
150 |
Noise-control techniques
There are four fundamental ways in which noise can be controlled:
reduce noise at the source, block the path of noise, increase
the path-length, and protect the recipient. In general, the
best control method is to reduce noise levels at the source.
There are four fundamental ways in which noise can be controlled:
reduce noise at the source, block the path of noise, increase
the path-length, and protect the recipient. In general, the
best control method is to reduce noise levels at the source.
However, one of the best methods of noise source reduction is
the regular and thorough maintenance of operating machinery.
Noise levels at construction sites can be controlled using proper
construction planning and scheduling techniques. Locating noisy
air-compressors and other equipment away from the site boundary,
along with creating temporary barriers to physically block the
noise, can contribute to reducing noise pollution.
Most of the vehicular noise comes from the movement of the vehicle
tires on the pavement and wind resistance. However, poorly maintained
vehicles can add to the noise levels. Traffic volume and speed
also have significant effects on the overall sound. For example,
doubling the speed increases |
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