Learning with Times: Why this Diwali could be good news for your ears, too

The Supreme Court issued guidelines ahead of Diwali to rein in pollution caused by fireworks, allowing only ‘green’ firecrackers. While doubt has been expressed over how effectively the SC order will be implemented, pollution levels during the festival show why strict regulation is desirable.

HOW IS NOISE MEASURED AND WHAT IS AMBIENT NOISE LEVEL?

Noise is measured in a relative unit called decibel (dB). Unlike metre and kg, which are absolute units, decibel is simply the ratio between two sound levels — measured sound pressure level at a point/time as compared to the minimum sound pressure level that a person with good hearing can detect. As sound levels may fluctuate, the best way is to measure it over a defined period, expressed in dB(A) Leq (A signifies weighted average).





WHAT ARE THE SOUND LEVELS CREATED BY VARIOUS HUMAN ACTIVITIES?

A person with normal hearing can detect sound between 0 dB to 140 dB. Sound between 120 dB to 140 dB can cause pain in normal people. The decibel scale is logarithmic and hence an increase of 10 dB will mean a 10-fold increase in sound level. Thus, a 20 dB increase will mean a 100-fold increase. When sound intensity is doubled, the increase is only by 3 dB. If a drilling machine is causing 80 dB noise then two machines with same noise level will have a combined effect of 83 dB.





HOW DOES AIR QUALITY CHANGE ON DIWALI?

If one looks at the Air Quality Index (AQI) data for different locations in Delhi, air on Diwali in 2017 was extremely polluted. For nearly all locations, AQI was at ‘very poor’ level.




HOW DOES THE AMBIENT SOUND LEVEL CHANGE ON DIWALI?

Taking only Delhi’s sound level during Diwali, there is a general increase of more than 20 dB(A) Leq for many stations as compared to the standard for ambient sound. This translates to a more than 100-time increase.




Research: Atul Thakur; Graphic: Karthic R Iyer