The study by the Brihanmumbai Municipal Corporation (BMC) has so far measured sound levels at 740 of 1,200 locations across the city. Municipal officials said most of the locations recorded noise levels above permissible limits for residential areas and silence zones.

“We have finished the mapping process for the island city and majority of the eastern suburbs. After the monsoon season, work will resume and locations in the western suburbs will be mapped,” said a senior municipal officer. “We found that a majority of the locations recorded noise levels at an average of 75dB during the day and 65dB at night, irrespective of silence or residential zones.”

According to Noise Pollution (Regulation and Control) Rules, 2000, residential and silence zones — areas around schools, hospitals and religious shrines — should have a maximum noise level of 55dB and 50dB in the day and 45dB and 40dB at night.

A report by the Central Pollution Control Board earlier this year said Mumbai is India’s noisiest city. Doctors said exposure to high noise levels causes hearing loss, high blood pressure and mental health problems . “Excessive noise from sources such as car horns can cause various health problems related to the heart and mind cancer,” said Dr John Panicker, national coordinator of Indian Medical Association’s Safe Sound Initiative.

“Exposure to noise pollution above 80 decibels (dB) for eight hours a day for eight years will induce permanent deafness. Shorter exposure of higher decibel levels also damages the ear drums,” said Dr MV Jagade, consultant ENT surgeon and head of department at JJ Hospital and Grant Medical College.

The noise-mapping project, which began in October 2015, is likely to be completed by December. The BMC has hired private consultants to study noise levels at around 50 places in each of the 24 municipal wards. “After collating the data, the consultant will then have to propose ideas and technologies to bring down noise levels by submitting a final report in January. It will help us narrow down on areas with high noise levels, and which may need sound barriers,” said the official adding that the project will continue after the monsoon season.

A recent Bombay High Court (HC) order from last month made it mandatory for all authorities to carry out noise mapping and take into account all aspects of noise pollution as a parameter of quality of life. The division bench of Justice bhay Oka and Justice Amjad Sayed said noise mapping should be carried out in all major cities of Maharashtra and integrated into the Development Plan.

“The state government shall consider undertaking exercise of noise mapping in all major cities in the state as availability of data obtained by noise mapping will help concerned authorities to discharge their duties. We direct the state government to take appropriate action within a period of two months from the date of the order,” read an extract from the order.

Former municipal commissioner V Ranganathan said both development plans prepared under the Maharashtra Regional Town Planning Act did not address the serious issue of noise pollution at all. “The government needs to identify primary sources for noise through this mapping process and highlight their significance in the DP. They need to find out what is being done abroad to mitigate such issues,” he said.

A CPCB analysis has found Mumbai to be the noisiest city in India after a series of regular ambient noise monitoring from 2011 to 2014. Noise monitored at five stations at Mumbai, Navi Mumbai and Thane saw four out five stations exceeding decibel levels as per noise standards laid down in Noise Pollution (Regulation and Control) Rules, 2000.

“In order to be useful for city planning and for integration into the DP, the noise map of the BMC needs to identify individual sources of noise including traffic, construction and noisy institutions. Zoning laws for construction of different types of infrastructure need to be appropriately based on the findings on the noise map, for example, a hospital cannot be placed next to a noisy restaurant or open ground where s school events take place,” said SumariaAbdulali, convener, Awaaz Foundation.

Why noise mapping?

Noise Mapping is an established method to capture existing noise levels and predict levels in case of change of land use like new infrastructure projects etc that helps municipal corporations differentiate between residential, silence and commercial zones in the city so that noise rules are not flouted.

Why did the civic body begin mapping noise?

The move came after several concerns were raised in the past regarding increasing level of noise pollution in the city. After an Environment Status Report 2012 recorded high noise levels across the city, the civic body failed to take substantial steps to curtail the increasing noise pollution due to lack of comprehensive data. Last year, a proposal was drafted worth Rs 61 lakh that was approved by a standing committee to complete the noise mapping project within 12 months starting October (excluding monsoon season).

How the study is being done?

The project aims collating sound levels and patterns across 1,200 locations in the city, of which 740 have been completed. The locations where the mapping is done were identified in October last year. The mapping process is done using four decibel metres at each location and the combined data will be analysed and interpreted in January by the private consultant.