Noise Reduction Rating - NRR 33 Decibels (when used as directed) Noise reduction rating: 33 Decibels (When used as directed). The range of noise reduction ratings for existing Hearing protectors is approximately 0 to 30 (higher numbers denote greater effectiveness) Information required by EPA: The level of noise entering a person's ear, when a hearing protector is worn as directed, is closely approximated by the difference between the A-weighted environmental noise level and the NRR. Example: The environmental noise level as measured at the ear is 92 dBA. The NRR is 33 decibels (dB]. The level of noise entering the ear is approximately equal to [92 dB(A) - 33] 59 dB(A).
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