If a worker wears both earplugs and earmuffs at the same time, how much increase would you expect in the Noise Reduction Rating (NRR)?
The OSHA Technical Manual allows employers to add 5 dB for the second hearing protector. An example: if wearing an earplug with an NRR of 25 together with an earmuff (also with an NRR of 25), expect a combined NRR of 30. Keep in mind, however, that this rule of thumb is a general estimate. To learn more about the ins and outs of dual hearing protection, and how to improve accuracy of your estimates, see this SoundBytes article.
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- My job can be boring. Is it OK if I listen to music headphones while I'm working?
- What is the Noise Reduction Rating?
- What is the Personal Attenuation Rating (PAR)?
- Why do OSHA formulas require us to subtract 7 dB from the Noise Reduction Rating (NRR)?