Noise Reduction Rating (NRR)

Noise Reduction Ratings are a unit of measurement used to reflect the effectiveness of hearing protection devices to decrease sound exposure. Ear plugs and ear muffs are sold with a noise reduction rating to indicate its level of protection; the higher the NRR the higher level of protection.

Using the NRR rating, ear plugs and ear muffs are classified by their potential to reduce noise in decibels within a given working environment. The approximate range for hearing protection sold in the United States extends from 0 to 33 decibels. To understand how much the hearing protector reduces the surrounding decibel level, take the NRR number, subtract seven and divide by two. Take that number and subtract it from the surrounding dB level to determine the new level of noise exposure.

If an employee is working on a site with a surrounding decibel level of 90dB, how much protection does a pair of NTRR 29 ear muffs provide? Following the above equation, we get an answer of 12 dB. This means when the worker is wearing this pair of ear muffs correctly, the new level of noise exposure will be 78 dB. Additionally, employees can also wear dual hearing protectors, like a pair of ear muffs worn over ear plugs. This will add five more decibels of protection to whichever one has the higher NRR.

Hearing Protection Devices

Using the NRR rating, ear plugs and ear muffs are classified by their potential to reduce noise in decibels within a given working environment. Ear plugs and ear muffs must be tested and approved by the American National Standards Institute in accordance with the hearing protection requirements from OSHA.

The approximate range for hearing protection sold in the United States extends from 0 to 33 decibels. To understand how much the hearing protector reduces the surrounding decibel level, take the NRR number, subtract seven and divide by two. Take that number and subtract it from the surrounding dB level to determine the new level of noise exposure.

The ANSI S3.19 standard established the Noise Reduction Rating but has since been superseded by the ANSI/ASA S12.6-2016: Methods for Measuring the Real-Ear Attenuation of Hearing Protectors. Under this standard, hearing protection is tested in sound rooms, individual variation is accounted for, and the rating is adjusted for “real-world” noise.

 
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