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.
The NoiseMeters NRR Calculator uses the following calculation
methods:
Regulation
Frequency
Weighting
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
