The Hindu : Karnataka / Bangalore News : The noise is more than you can bear

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Sunday, Jul 08, 2007
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Karnataka - Bangalore

The noise is more than you can bear

Govind D. Belgaumkar

The levels are much higher than those prescribed by Pollution Control Board: BMRC study

BANGALORE: You are hearing a lot more noise than your eardrums can take.

A year-long study by Bangalore Metro Rail Corporation (BMRC) between January and December 2006 has found that noise levels in many key junctions are far higher than those prescribed by the Central Pollution Control Board (CPCB).

For example, the noise level is some 80 decibels during the day at two of the 17 areas studied — the junction of Ring Road and Tumkur Road (Goraguntepalya) and Majestic Circle.

Commercial category

The CPCB norm for commercial areas is 65 decibels during day and 55 decibels during night and all the areas surveyed predominantly fall under the commercial category.

In fact, the study showed that the noise level is beyond 65 decibels during the day in all the 17 spots selected along the proposed Metro route. Invariably, the readings were at least 10 decibels higher than the allowable levels. The same is the case with the noise levels during night — some decibels higher than the permissible limit of 55.

World Health Organisation’s (WHO) studies on community noise have found that even a level of 50-55 decibels can cause “annoyance” in outdoor living areas while 70 decibels can result in hearing impairment in traffic and commercial areas. Noise above 80 decibels may increase aggressive behaviour, according to it.

People living close to these noisy traffic areas are apparently at a health risk considering WHO’s findings: “Prolonged or excessive exposure to noise, whether in the community or at work, can cause permanent medical conditions, such as hypertension and ischemic heart disease.”

Mental health

What is more, it has found “a link between community noise and mental health problems” going by the “demand for tranquillisers and sleeping pills, the incidence of psychiatric symptoms and the number of admissions to mental hospitals.”

Why did BMRC study noise levels?

It was conducted to get basic data to assess the future impact of metro rail during and after its construction. “The noise assessment will be based on the expected change in the existing noise levels…A noise survey will be undertaken to determine the ambient noise environments along the route,” BMRC sources said.

A Bangalore University team, led by R.K. Somasekhar of the Department of Environmental Sciences, studied the noise levels. Studying noise is not easy.

Most environmental sounds are made up of a complex mix of different frequencies. Hence, the scientists studied noise levels for different frequencies grouped as L{-1}{-0}{-,} L{-5}{-0}{-,} L{-9}{-0}{-,} L{-m}{-a}{-x} and L{-d}{-n} in addition to studying day and night levels.

The WHO describes L{-1}{-0} as the sound pressure level that is exceeded for 10 per cent of the time for which the given sound is measured and L{-m}{-a}{-x} as the maximum sound level. L{-d}{-n} is day-night sound pressure level with a 10 dB night-time weighting.

For easier understanding, only the day and night recordings are considered in this report.

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