Deafening Noise

Constant exposure to noise can make one deaf. The major culprit is road traffic. Can one avoid noise? It’s difficult. Checking it, however, is not impossible. As the Central Pollution Control Board regulations remain unimplemented, the authority has initiated a nationwide real time noise monitoring, hoping for an improvement. Sayantan Bera in Kolkata, Ankur Paliwal in Delhi and Sumana Narayanan in Chennai report on the increasing noise levels

By Sumana Narayanan, Ankur Paliwal, Sayantan Bera
Published: Friday 30 September 2011

Deafening Noise


Ask Priyabrata Kanjilal, a grocery store owner in one of the bylanes of south Kolkata, for a Vim washing bar. Chances are he will produce an egg (dim in Bengali), for he cannot distinguish between the two words. Twenty years at the store has taken a toll on his hearing ability. During his eight hours at the store it’s not the good old radio that he listens to, but the steady groan of traffic on the 4.5-metre alley. Impatient honks and noise of trucks, buses, autorickshaws, cars and bikes are a constant. The 50-year-old is also a captive listener of the many religious, social and political processions that often pass through the road, all expressing their emotions through blaring loudspeakers.

At home his family complains he talks too loudly and turns volume of the television too high. He gets angry easily, suffers from sleep disturbance, recurring headaches and occasional vertigo.

How noise impacts hearing
  A bed of grass, trampled by a morning walker, straightens up in a while. But after a few days of regular walking, it withers and dies. Loud sound or noise does something similar to the ear. Death of a hair cell is permanent. When too many of them die, one would require a hearing aid.

Sound travels in mechanical vibrations through the external auditory canal and reaches cochlea, the auditory portion of inner ear. Each cochlea has 18,000 hair cells, so small that all of them can fit on a pinhead. It is the job of these extremely delicate and sensitive hair cells to transform the mechanical energy of the vibrating sound waves to a nervous impulse which, in turn, is processed by the human brain. Thus we hear—the rustling of leaves, whispers, cries and conversations, the rhythmic beats inside a night club, or the painful orchestra of a hundred honks on a choked highway.

On the insistence of Down To Earth, Kanjilal underwent a pure tone audiometry. This simple test is done in a sound-proof room where the patient is made to hear sounds of different frequencies. The audiologist increases the sound until it becomes audible to the patient.

A normal human being can hear a 4,000-hertz tone at 20 decibels. Kanjilal could hear it at 50 and 55 decibels in his right and left ears respectively. His hearing loss is more pronounced at higher frequencies, suggesting a case of noise-induced hearing loss (NIHL). It is scientifically taken that NIHL affects higher frequencies first.

Kanjilal’s loss is irreversible. Continuous exposure to noise will gently kill all the tiny hair cells inside his cochlea, the auditory portion of the inner ear (see ‘How noise impacts hearing’ on p30). “Avoid noise,” recommends his medical report. But he cannot stop going to his shop.

“As a society, our tolerance to noise is phenomenal. We seldom mind loud music, honk indiscriminately, and while working in heavy industries rarely ask our employers to give us protective devices,” says Somnath Mukherjee, audiologist at Apollo Hospital in Kolkata.

This, despite Kolkata being the first city in India to legislate on noise. Taking up noise as a subject that needs to be urgently addressed, Calcutta High Court judge Bhagabati Prosad Banerjee has passed some pioneering judgements. These were also inspired by the writings of Narayan Ganguly, a Bengali author.

imageIn November 1970, the ailing author wrote in his satirical column, Sunondo’s Journal, for a literary magazine: “Even today, there was no respite from the demonic duet of loud music and firecrackers. Perhaps I still have a few days left to eat and breathe, so I haven’t had a heart attack yet…. Heard there is some law regarding amplifiers, but that must be a rumour.” The column, published after Ganguly’s death, left a deep impression on Justice Banerjee. “I started reading on noise pollution after his death—the legal and regulatory history around the world. And then I actually waited for a case,” he says with a smile.

In 1996, Om Birangana Religious Society filed a petition in the Calcutta High Court complaining the police was stopping it from using microphones to play religious songs. A few months later, Justice Banerjee pronounced a landmark judgement. “Freedom of speech and expression includes, by necessary implication, freedom not to listen and/or to remain silent… One cannot exercise his right at the cost of and in total deprivation of others’ rights,” he ordered.

For the first time in India use of microphones was banned during night hours—from 9 pm to 7 am.

image“During my tenure, I disposed of noise-related cases regarding violation of court orders every Friday. I also directed the police and the West Bengal Pollution Control Board (WBPCB) to register the complaints anonymously. This encouraged people to lodge complaints,” Justice Banerjee says. His orders helped Kolkata become a better monitored place. The city has improved. WBPCB data shows a drop of about 10 decibels from 1994 to 2009. But it is not enough when the noise level is compared to the ambient noise standards.

Painful noise

The impact of rise in noise level is visible countrywide. According to a 2007 world health organization (WHO) estimate, almost six per cent people in India suffer from hearing loss. This, when hearing loss is not monitored regularly in the country.

imageA human ear can detect the rustle of leaves at 10 decibels, hear a conversation at 60 decibels and even sustain the constant rhythmic thudding noise inside a night club at 110 decibels. Sound becomes painful as it reaches 120 decibels. Chronic exposure to sound beyond 85 decibels for eight hours can cause irreversible hearing loss. A 140-decibel sound impulse next to the ear can tear the eardrum.

Every increase of 10 decibels makes the sound twice as loud to the human ear. For every three decibel increase in sound after 85 decibels, the safe exposure time gets reduced by half. For instance, if 85 decibels is safe for eight hours, 88 decibels will be safe only for four hours.

About 120 decibels sound is safe only for seven seconds. Wondering how then disc jockeys survive? Well, they wear ear plugs as precaution.

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