Hearing Protection Advice
By: Clark Vargas, P.E.
If you are at an outdoor range, exposed to a considerable volume of gunfire 130 to 125 dB at the lug holes double plugging is about the only solution outdoors in terms of effective hearing protection.
Some of the passive and electronic muffs offer a 26dBA overall SNR reduction which simply is not enough: can still end up being exposed to 104-99dBA on the firing line. The Peltor ProTac gives 32dBA SNR reduction is better, but still not good enough if exposed all day.
The effect is cumulative and long term exposure to 85 dBA or above can cause temporary or permanent hearing loss and triggers an OSHA action level so higher sound level = lower time period of safe time exposure. This is roughly how it goes:
OSHA’S TABLE G-16 PERMISSIBLE DAILY NOISE EXPOSURE
Length of time, Hours/Day Noise Level, dBA
So 90dB at the lugholes is what you need to aim for if you are going to be on an outdoor firing line all day.
Even the highest rated passive muffs are not going to get you there for extended use: the Peltor Optime III (which is same as the Bullseye III) gives 35dB SNR reduction. Earplugs can give 35+dB SNR if fitted 100% correctly, hence the attraction of custom fitted jobbies. The foam disposables can give 30dB SNR reduction. So a cheap and easy fix one would think is to use foam plugs (-30dB) under the less expensive active slim line muffs, (26dB) reduction and with the plugs one would think easily gets to around 56dB reduction not so SNR values are all ready log qualities and doubling the value only increase protection by 3dBA. Assuming 127.5 dBA at the line it double reduces sound pressure (-29dBA) to 98.5 dB’s at the ear, much better but you should not be expose more than 3 hrs according to the above table.
Of course then you will not hear normal speech, you have to turn the volume up on the muffs up a bit so you can hear speech, commands etc whilst the muffs will of course cut out the peaks.
The above does not apply to indoor ranges which if untreated reverberate for 6 or more seconds.