Hearing Protector Use & Care

If your company uses A-weighting to measure the TWA noise exposure of employees, the OSHA method for determining adequacy of hearing protection using the NRR is shown in Example 1 above.

In Example 1, the protected exposure for a group of employees who wear this hearing protector is estimated to be 71 dBA. This protected exposure level is well below the OSHA PEL of 90 dB TWA so the hearing protector attenuation would be considered adequate for this exposure.

NOTE: When C-weighting is used to measure the TWA of employees, OSHA does not require use of the 7 dB correction to the NRR.

The practice of reducing the NRR value, or derating, is done to account for the difference between the NRR and the attenuation workers get when on the job. Since the 1980s, OSHA enforcement policy in the U.S. has been to apply a 50% derating to the NRR as a safety factor when employers use hearing protectors as a substitute for noise controls. See Example 2 to learn how to apply the OSHA 50% derating.

In Example 2 above, the protected exposure for a group of employees who wear this hearing protector is estimated to be 83 dBA. This protected exposure level is below the OSHA PEL of 90 dB TWA so the employer who uses this hearing protector as a substitute for noise controls would likely be considered to be in compliance with OSHA noise control requirements.

Wearing earmuffs together with earplugs provides between 5-10 dB more noise reduction than either device worn by itself. The extra protection provided varies depending on the frequency of the sound.

In the U.S., OSHA allows employers to add 5 dB to whichever device has the highest NRR to estimate the combined protection when dual protection is worn. In most cases, this 5 dB adjustment is factored in after the NRR has been corrected for A-weighting and derating has been applied. See Example 3 above.