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hksigwalther · October 8, 2001, 11:50 AM

[Speculation]

I'm pretty sure the NRR is on the decibel scale. So, for example, a .22lr at 120 dB will be reduced to 95 dB with 25 NRR plugs.

I don't see why the ratings would not be added if using two forms of protection at the same time. If the first line, like ear muffs, has an NRR of 30 the .22lr would sound like 90 dB on the inside of the muff. When those sound waves hit the second line, say foam ear plugs, with an NRR of 25 at 90 dB, then the side noise should be reduced to 65 dB when it hits your eardrum. This would be the same as NRRs of 30 + 25. 120 dB - 55 = 65 dB.

October 8, 2001, 11:50 AM	#2
hksigwalther Senior Member Join Date: November 18, 1998 Location: NE OH, USA Posts: 3,198	[Speculation] I'm pretty sure the NRR is on the decibel scale. So, for example, a .22lr at 120 dB will be reduced to 95 dB with 25 NRR plugs. I don't see why the ratings would not be added if using two forms of protection at the same time. If the first line, like ear muffs, has an NRR of 30 the .22lr would sound like 90 dB on the inside of the muff. When those sound waves hit the second line, say foam ear plugs, with an NRR of 25 at 90 dB, then the side noise should be reduced to 65 dB when it hits your eardrum. This would be the same as NRRs of 30 + 25. 120 dB - 55 = 65 dB. __________________ - Ron V.