Information for Shooters
Lipin/Dietz Associates, Inc.
In most cases, the sound level from firing a weapon is sufficient to require the use of hearing protection, even if the weapon is fired only one time. Recent NIOSH studies of sound levels from weapons fires have shown that they may range from a low of 144 dB SPL for small caliber weapons such as a 0.22 caliber rifle to as high as a 172 dB SPL for a 0.357 caliber revolver.
NIOSH recommends that hunters and shooters use double hearing protection each
and every time a weapon is fired. Double protection involves wearing both
earplugs and earmuffs. The best combination is a deeply inserted foam earplug
and a well-seated earmuff.
The formula for
determining the maximum number of shots is:
where pldB is the peak level of the sound in the ear canal under the earmuff and earplug. NIOSH recommends that peak exposures be limited to one event not exceeding a peak level of 140 dB SPL. That is, exposure to one event of 140 dB SPL would constitute 100% of a persons’s noise burden.
As shown in Figure 2, the amount of reduction for 12-gauge shotgun using the David Clark Model 27 earmuff is 31 dB, reducing the peak level from 161(red line) to 130 dB SPL( blue line). So, with the earmuff alone, the number of shots recommended by NIOSH would be five per 24-hour period. The addition of a deeply inserted foam earplug reduces another 21 dB, increasing the allowed number of shots to more than 1200 per 24-hour period. A smaller caliber weapon with a lower peak level, such as 0.22 caliber rifles with peak levels of 144 dB SPL, could be fired as many as 63000 rounds per 24-hour period if the shooter were to wear an active level-dependent earmuff along with a deeply inserted foam earplug. The combination of an earmuff and a deeply-inserted foam earplug can provide as much as 50 dB of peak reduction, which is adequate in most cases.
Double hearing protection can severely compromise the ability to communicate when both devices are passive, linear protectors. The use of an active level-dependent earmuff with a deeply-inserted foam earplug can compensate for the loss of communication ability when double protected. In some cases, the earmuff may provide sufficient gain to counter the attenuation of the earplug.
For shooters, a key indication that whatever protection is being used is inadequate is ringing of the ears or a feeling of fullness in the ears after an episode of shooting.
There are also active level-dependent hearing protectors that are built into pre-molded earplugs and custom earplugs as well on the market. There are no data on their effectiveness. At present, there are no data on the use of an active level-dependent earplug in combination with a passive earmuff. Given the attenuation chain, it is doubtful that the pairing would be as effective as the active level-dependent earmuff with foam earplug.