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STW
October 3, 2008, 02:20 PM
I use muffs rated at 33dB. I also use ear plugs. Lets say they are rated at 25 (I actually don't know).

Is there a rule that tells me the cumulative effect of both muffs and plugs?

I know it's not additive, particularly since dB are logarithmic. However, being logarithmic even a 3dB increase would be huge.

WESHOOT2
October 5, 2008, 08:17 AM
Wearing both (of decent-or-better quality) means no worries.

I use 33db plugs, and numerous muffs of differing ratings (but mostly 21s).

Double Naught Spy
October 5, 2008, 12:18 PM
If worn properly, the plugs will block 33 db of the noise that reaches them from getting into the auditory canal. How much sound that reaches them will depend on how much bypasses the muffs.

I used to wear passive 30 db nrr muffs and 33 db nrr plugs and have trouble hearing anyone who wasn't shouting at me or looking right at me when they spoke.

I now use electronic muffs to overcome the combined efficiency of muffs and plugs so that I can hear normal conversation.

I like Weshoot2's formula.