# Why is doubling up with plugs and muffs when shooting not more effective?

I keep looking for better ways of protecting my hearing when shooting, and it looks like wearing both plugs and muffs is recommended for indoor shooting (centerfire gunshots range from 160-170 decibels).

However, if you look at the OSHA recommendations, one will notice that they say that doing so only adds,

Note: 5 dB can be added to the NRR of the most protective device when using both earplugs and muffs.

Given that earplugs often have a NRR of 32 decibels and muffs 22-28 decibels, why is doubling up not more effective?

Wouldn't the noise be reduced by 22 decibels by the muffs and then 32 by the plugs instead of just 5 more decibels?

• Commented Dec 10, 2018 at 17:23
• @topshot Are you going to make that an answer, or would you care if I self answer from that article? Commented Dec 10, 2018 at 17:25
• Feel free to self answer Commented Dec 10, 2018 at 17:37
• Perhaps you already know, but since decibels work on a logarithmic scale, a 5 dB reduction is still nothing to sneeze at! That’s still a roughly 70% reduction in volume. Commented Dec 11, 2018 at 6:01
• @SebastiaanvandenBroek depends what you mean by volume :) The sound intensity drops by 70%, but the sound pressure would only drop by less than 50% and the loudness would change by even less. With OSHA, a 5 dB reduction, roughly doubles the time you can be exposed. Commented Dec 11, 2018 at 12:51