NRR, a.k.a. Noise Reduction Rating
The NRR is a single-number rating method which attempts to describe a hearing protector based on how much the overall noise level is reduced by the hearing protector. When estimating A-weighted noise exposures, it is important to remember to first subtract 7dB from the NRR and then divide the remaining number by 2.
(i.e.: NRR=30dB – 7dB = 23/2 = 11.5 dB of noise protection)
Recommended Selection
Ear Muffs
Muffs tend to be the most reliable in terms of employees using them as they are fairly easy to put on. However due to the fact they can be hot, heavy and uncomfortable, they are often not the first choice for workers. Ear muffs require annual maintenance by replacing cushions which may crack or lose their resiliency. The seal between the cup and the head is critical for providing the proper protection. The use of perspiration pads will improve the comfort of the muffs in warm environments.
De-rate NRR by 25%
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Foam Plugs
These are an excellent form of hearing protection when worn properly. If they are worn
incorrectly, the required attenuation will not be provided to the individual therefore defeating the purpose of using them. They are cool and comfortable to wear and are meant for all day use. They should not be removed repeatedly throughout the day. They are useful in extremely dirty environments or where employee’s hands get quite dirty. Employees must be taught the proper use of this product for it to be effective.
De-rate NRR by 50%
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Standard Ear Plugs
These plugs are a bit easier to put in than a foam plug but they are not as effective. The plugs come in a variety of sizes and the employee must be given the correct size for them to work properly. They tend to be cool, comfortable, and inexpensive and can last up to 6 months.
De-Rate NRR by 70%
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Ear Bands
These semi-aural protectors look like earplugs with a headband and are lightweight. They are convenient for short wearing periods where protection is taken on and off frequently. They are not intended to be worn for long periods, particularly in high noise areas. Their use is limited and therefore not as popular as ear muffs or foam plugs.
De-rate NRR by 70%
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