Noise Monitoring and Noise Survey

Two different noise questions

Industrial sites face two separate obligations, and they are routinely confused:

• Ambient noise - what the plant emits into its surroundings, governed by the Noise Pollution (Regulation and Control) Rules, 2000, with separate day and night limits by area category
• Workplace noise - what operators are exposed to, governed by the Factories Act and its state rules, measured as an eight-hour equivalent exposure

A site can comply at the boundary and still be exposing operators well beyond the limit. The two need different instruments, different sampling and different corrective action.

What a noise survey covers

• Day and night ambient measurement at the boundary and at nearby receptors
• Workplace dosimetry for operators on high-noise equipment
• Octave band analysis, which identifies the frequency causing the problem and therefore what will actually attenuate it
• Noise contour mapping across the plant, so control effort goes where exposure is
• A control plan - enclosure, damping, relocation or PPE, in that order of preference

Why octave band analysis matters

An overall dB(A) figure tells you there is a problem, not what to do about it. Low-frequency noise from a large fan passes straight through an enclosure designed for high-frequency noise. Measuring by frequency band is what turns a compliance number into an engineering decision.