Скачать или смотреть SOURCES OF NOISE POLLUTION

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 industries 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, neighborhood 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.



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