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Occupational Noise Calculators

NRR - Noise Reduction Rating - Help

All hearing protectors supplied in the USA should be provided with an NRR figure. It can be used to estimate the sound level at the ear when wearing the protectors.

To calculate the level at the ear, fist measure the worker's noise exposure, either in dB(A) or dB(C). This level can be entered into the NRR Calculator, along with information about the regulations that you are following: OSHA or NIOSH as each of these uses a different calculation.

nrr calculator

The NoiseMeters NRR Calculator uses the following calculation methods:

Regs Freq.
Wgt
Calculation
     
OSHA A Lprot = L - (NRR - 7) / 2
  C Lprot = L - NRR / 2
     
NIOSH A Lprot = L - (NRR - 7)
  C Foam Earplugs:
  Lprot = L - (NRR * 0.5)
    Other Earplugs:
  Lprot = L - (NRR * 0.3)
    Earmuffs:
  Lprot = L - (NRR * 0.75)

Where:

L is the measured level or TWA
NRR is the Noise Reduction Rating provided by the hearing protector manufacturer
Lprot is the estimated sound level at the ear when wearing the hearing protection

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