Annex 2 of NR15 – Tolerance Limits for Impact Noise

1. Peak acoustic pressure emanating for a duration less than one second at intervals greater than one second is considered as impact noise.

2. The impact levels shall be measured in decibels (dB) with a sound pressure level meter in linear and impulse response mode. The readings shall be made near the ear of the worker. The tolerance limit for impact noise will be 130 dB (linear). In the intervals between the peaks, the existing noise shall be evaluated as continuous noise.

3. In case of unavailability of a sound pressure level meter with impulse response, it shall be valid to read in rapid response (FAST) and C-weighted. In this case, the tolerance limit will be 120 dB(C).

4. The activities or operations that expose the workers, who are without adequate protection, to the impact noise levels greater than 140 dB (LINEAR) measured in impulse response, or greater than 130 dB(C) measured in rapid response (FAST), pose an imminent and serious danger.