Previous Year Question

Noise Pollution refers to the presence of unwanted or excessive sound in the environment that may affect human health, comfort, communication, and daily activities. In this question, sound above 80 decibels (dB) is considered to fall within the category of hazardous noise pollution.

Decibel (dB) is a logarithmic unit used to express sound levels. The Sound Intensity Level is expressed by the following formula—

β = 10 × log₁₀(I/I₀)

Here, β represents the sound intensity level, I represents sound intensity, and I₀ = 10⁻¹² W/m² is the standard reference intensity.

An increase of 10 dB represents a tenfold increase in sound intensity. Similarly, an increase of 20 dB represents a hundredfold increase in intensity. However, Perceived Loudness and physical sound intensity are not identical concepts.

Common examples of different sound levels:

Noise-Induced Hearing Loss does not depend only on sound level but also on Exposure Duration and repeated exposure. According to the US National Institute for Occupational Safety and Health (NIOSH), a recommended occupational exposure limit of 85 dBA is specified for an eight-hour daily average. The permissible exposure duration decreases as the sound level increases.

In India, different noise limits have been prescribed for different areas under the Noise Pollution (Regulation and Control) Rules, 2000.

These limits are based on the Equivalent Continuous Sound Level (Leq) over a specified period. Therefore, 80 dB should not be treated as the only legal or medical threshold for noise pollution under all circumstances.