![]() Table 10.1: Some Typical Industrial Noise Levels Some typical industrial noise levels are given in table 10.1. For example, the workers near the heavy industrial blowers in steel industry are exposed to sound of 112dB for eight hours and hence suffer from occupational pollution. The noise pollution is further magnified due to the installation of industries in compact places. The operations in pneumatic drills, milling machines, cutters, printing press with an upward, downward and sideways movement and vibrations, cause lowering of hearing capacity to a large extent. Some industrial processes like weaning, ship building, boiler making, pressing and blasting operations are more nosier than others. The different machines of numerous industries, factories and mills produce a lot of high intensity sounds causing noise pollution. Sonic boom occurs when an aircraft flies supersonically overhead. Sonic boom is an important aspect of aircraft noise. Jet engines create most noise around a radius of 16 km. Noise generates from compressor and turbine and near jet exhaust. Larger and faster aircrafts produce high noise intermittently during takeoff, landing and during flight. Besides use of welded tracks and improved coach suspension have contributed to the reduction in railways noise, Introduction of diesel engines or electrical engines has reduced the intensity of rail traffic noise which was previously shown by steam engine. The noise from rail traffic is comparatively lower than that from road traffic. Faster moving vehicles produce high noise from their gear box, exhaust system, vibrations from their body, etc. The chief causes of road traffic noise are the number of road vehicles and their high traffic speed. The transport noise includes road traffic noise, rail traffic noise and aircraft noise. The main threat of noise comes from transport sector. It may be noted that the manmade noise is now doubling after every decade.īroadly speaking, the noise may be classified into: The manmade noise are mechanized automobiles, industries, trains, aero planes, social functions etc. The natural sources of noise include thunder, cyclone, roaring of sea, etc. Noise may originate either from natural sources or from anthropogenic activities. So, sound of more than 130 dB causes noise pollution. Sound intensity of 130 dB is the upper limit of the threshold of hearing and beyond this, is the threshold of pain which may cause damage to car and leading to hearing impairment. The sound intensity from 0 to 100 dB is pleasant but when the sound intensity exceeds 120 dB, it causes noise. The unit of sound intensity is decibel (dB). ![]()
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