In India, at present, there is no separate regulation for noise control. However, it is expected that suitable parameters, i.e., noise level and frequency, will be prescribed both for ambient conditions as well as industrial environment, particularly engineering as well as fabrication industries.
Noise pollution from vehicles is important, particularly in metropolitan areas. Noise directly affects the senses and, consequently, the quality of the urban environment, more than any other nuisance, stemming from technical progress.
Urban noise is an erratic combination of ‘peak noise’ and background noise of a lower intensity ranging from about 50 to 70 dB (A), for which motor vehicles are regarded as one of the major contributors.
Image Source : environment-today.org
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This is in spite of the significant progress achieved in the last decades in silencing exhausts and reducing mechanical noise, in developed countries. Noise disturbs sleep and may be a cause of stress.
The noise-control levels enforced in Europe, Japan and the USA generally result in a minimum of exhaust pipe noise, achieved by means of advanced silencers, using gas expansion and noise frequency interference techniques. It may be difficult, technically, to further reduce this source of noise. Conversely, exploration of ways and means to reduce the following acoustic energy emissions and radiations which are unrelated to exhaust should continue:
(i) Fan aerodynamic noise, particularly from air-cooled engines,
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(ii) Mechanical noise from engine cylinder block and crank case, gear box transmission and alternators,
(iii) Rolling noise from tyres in contact with the road.
Diesel-equipped vehicles are noisy due to the nature of the engine combustion under very high compression. Public transport and heavy commercial vehicles require special consideration. Particular attention to their proper maintenance and periodic inspection, including their silencing devices, should be paid.