The term noise is derived from the Latin word
Nausea refering to the feeling of
sickness in the stomach with an urge to vomit. Any unpleasant and unwanted
sound is considered as noise. It is one form of pollution. Noise pollution can
be defined as unwanted or offensive sounds that unreasonably intrude into our
daily activities. It is responsible for various adverse effects. In recent
years noise is recognized as a major pollutant on par with other chemical
pollutants of air, water and biosphere. Noise has many harmful effects on man
and the damage incurred is irreversible.
There are various sources of noises and the
sources are broadly classified into industrial sources and non industrial
sources. The noise dumped into the atmosphere by the industires due to the
functioning of machineries form the industrial sources. On the other hand the
noise associated with urban development; road, air and rail transport; loud
speakers, radio and television stations, construction sites, neighbourhood and
recreational noise levels, and activities associated with urban living
generally lead to increased noise levels.
Sound is measured by several complex systems.
The best known unit of measurement is the measurement of sound in decibel which is named after Sir Alfred
Bell. The industrial noise survey of India recognized noise levels from 81dB to
120dB as permissible levels.
Loud noises (above 130 dB) can cause
immediate and permanent damage to the muscles in the middle ear, altering the
stiffness of the ossicles, damaging the hair cells of the cochlea and casuing
the rupture of ear drum thereby reducing the efficiency of hearing.
Prolonged exposure to
unpleasant noises may lead to severe mental distubances and violent behaviour.
Noise is also partially responsible for the increased consumption of alcohol,
drugs, tranquillzers and sleeping pills. Noise pollution further contributes to
a few cardiovascular problems. Peptic ulcers and asthma are aggravated. Small
vessels to glomerular circulation are subjected to vaso constriction and
ultimately the output of urine is reduced. Persons exposed to excessive noise
at work place have temporary impairment of hearing.