Hearing
The mechanism for chronic exposure to noise leading to hearing loss is well established. The elevated sound levels cause trauma to the cochlear structure in the inner ear, which gives rise to irreversible hearing loss. The pinna (visible portion of the human ear) combined with the middle ear amplifies sound levels by a factor of 20 when sound reaches the inner ear. In Rosen's seminal work on serious health effects regarding hearing loss and coronary artery disease, one of his findings derived from tracking Maaban tribesmen, who were insignificantly exposed to transportation or industrial noise. This population was systematically compared by cohort group to a typical U.S. population. The findings proved that aging is an almost insignificant cause of hearing loss, which instead is associated with chronic exposure to moderately high levels ofenvironmental noise.
Sources of noise
Where does it generate from? The sources of noise may vary according to daily activities. They sources may be domestic (movement of utensils, cutting and peeling of
fruits/vegetables etc.) natural (shores, birds/animal shouts, wind movement, sea tide
movement, water falls etc.), commercial (vendor shouts, automobiles, aeroplanes,
fruits/vegetables etc.) natural (shores, birds/animal shouts, wind movement, sea tide
movement, water falls etc.), commercial (vendor shouts, automobiles, aeroplanes,
marriages, laboratory, machinery etc.) industrial (generator sets, boilers, plant operations,trolley movement, transport vehicles, pumps, motors etc.). The noise levels of some of the sources are summarised at table 1.Typical surveys pertaining to causes of noise pollution, reveal the various sources of noisepollution and frequency variation of their occurrences. The results of a survey conducted in Central London, way back in 1961-62 reveals the presence of noise pollution even in theearly ‘60s . Road traffic is identified as the major source of noise pollution while at home or outdoors or at work.
Table 1 Typical noise levels of some point sources
Source | Noise level dB(A) | Source | Noise level, dB(A) |
Air compressors | 95-104 | Quiet garden | 30 |
110 KVA diesel generator | 95 | Ticking clock | 30 |
Lathe Machine | 87 | Computer rooms | 55-60 |
Milling machine | 112 | Type institute | 60 |
Oxy-acetylene cutting | 96 | Printing press | 80 |
Pulveriser | 92 | Sports car | 80-95 |
Riveting | 95 | Trains | 96 |
Power operated portable saw | 108 | Trucks | 90-100 |
Steam turbine (12,500 kW) | 91 | Car horns | 90-105 |
Pneumatic Chiseling | 118 | Jet takeoff | 120 |
Mumbai plans to mark 'No Horn Day' on April 7
