Noise pollution may be defined as the state of discomfort and restlessness to human beings caused by unwanted high intensity sound (noise). It is of both natural and artificial type. Former is caused by natural sources like cloud thunder, hailstorms, waterfalls, avalanches and landslides etc.
Latter is the outcome of human activities like running of machines, automobiles, aircrafts, radios televisions, exhaust-fans, lawn-movers, blowing of sirens, loudspeakers, and organising cultural programmes, dance, and music etc. It is the artificial noise pollution, which is increasing due to growing urban and industrial activities and is a matter of serious concern.
Noise level is measured in terms of decibel (dB) which is the unit of measurement of intensity of sound. A noise of zero dB on the decibel scale represents the faintest sound audible to human ear while that of 180 dB shows the sound of large rocket engine. In general, noise above 70 dB is harmful to human beings.
In India noise pollution is growing in recent years due to increase in industrial, urban, transport and construction activities. A number of studies have revealed that noise pollution is a greater menace in most of the million cities of India characterized with high traffic density and .industrial activities. However, the level of pollution varies in accordance with the location, time, population density and functions of the city.
The study of Kanpur (Kumra, 1982), Mumbai and Chennai have revealed common features, i.e. high noise level in the areas located close to aerodromes, railway stations, bus terminals, industrial establishments, busy markets, high density traffic routes and high population density clusters. Loudspeakers and traffic noise is the great nuisance in the Indian cities. The level of pollution increases during festivals, cultural programmes, elections, national festivities and victories and traffic jams.
Most of our cities have higher level of noise pollution than the permissible limit of 60-70 dB. Delhi (89 dB), Kolkata (87 dB), Mumbai (85 dB), Chennai (82 dB), Kochi (80 dB), Madurai (75 dB), Nagpur (75 dB) and Thiruvananthapuram (70 dB) may be cited as examples. A study by the Environmental Monitoring Laboratory of the Industrial Toxocology Research Centre (Lucknow) has shown that noise level is higher than 90 dB near Hazaratganj crossing, King George Medical College, NurManzil, Royal Hotel crossing, Gol Darwaza, Naka Hindola, Charbagh railway station, Lalkuan, Aminabad and Sadar crossing.
Continuous and prolonged exposure to noise polution causes several disorders and ailments in human beings which ranges from mild annoyance, mental tension, headache, fatigue, irritation, high blood pressure, stomach trouble, psychological problems, low working efficiency, and traffic accidents to permanent deafness.
According to a study conducted in five southern cities including Chennai, Coimbatore, Madurai, Kochi and Thiruvananthapuram to find out the Noise Induced Hearing Loss (NIHL) among the workers in the textile, automobile, oil, fertilizers and chemical industries, one out of every four workers suffered from incurable NIHL.
Further in these cities about 10 per cent of the people' such as traffic constables and pavement vendors, who were exposed to traffic noise, also had NIHL (Singh and Sinha, 1983, p.356). About 60 per cent of the students in the age-group of 5-10 years living in industrial areas, railway stations and other areas of high intensity noise cannot concentrate on their studies.