Tuesday, July 24, 2007

Whole lotta noise

Whole lotta noise
Traffic is pushing up city’s noise levels. Bansy Kalappa elucidates the causes and effects of this problem

Sound pollution in many places in Bangalore has increased 200 per cent in about five years, according to a survey carried out recently at 60 locations. The previous survey was conducted in 2002-03.
The worst-hit areas are the St John’s Hospital/Madiwala Junction, where peak noise levels reached 95 decibel (dB), an increase of 200 per cent. At Gandhi Bazaar and Ramakrishna Mutt, largely residential areas, the peak noise level was 94 dB — an increase of 150 per cent. Noise levels at Kempegowda Junction, too, peaked at 94 db, a 200 per cent increase. The highest noise level was recorded near St Martha’s Hospital at 96 dB.
The worst-offenders are blaring horns, which emit high frequency sounds which are harmful as they emit high pitch sounds over a very short period of time. Modified silencers in autorickshaws, motorbikes and badly maintained trucks are also major causes.
A eight-member team from N V Dynamics conducted the survey. Team leader Balamurali Krishna said: “A 200 per cent increase in noise levels means there is a significant increase in the pressure on the human ear. The way noise is generated and the way human ear perceives it are different; the human ear is frequency-dependent.’’
Average noise levels are calculated using data of recordings over several minutes of exposure to varying traffic conditions in periods lasting 15 minutes per session over three sessions. That adds up to about 45 minutes during peak traffic hours. The survey was done using a precision sound level meter and a digital data acquisition system. Those exposed regularly to such levels of noise risk suffer from hearing loss, sleep deprivation, chronic fatigue, anxiety, hostility, depression and hypertension. Pregnant woman, infants and children are particularly susceptible to continued exposure. Affected children can end up being slow learners.
The findings were presented to the police recently and they have promised to forward it to the pollution control board. The survey also warned Bangaloreans that pollution levels would touch an ‘intolerable’ 100 db across the city in three years if corrective action was not taken.


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