Auditory risk to unprotected bystanders exposed to firearm noise

What is the risk of hearing loss for someone standing next to a shooter? Friends, spouses, children, and other shooters are often present during hunting and recreational shooting activities, and these bystanders seem likely to underestimate the hazard posed by noise from someone else's firearm. Hunters use hearing protection inconsistently, and there is little reason to expect higher use rates among bystanders. Acoustic characteristics and estimates of auditory risk from gunfire noise next to the shooter were assessed in this study.

This was a descriptive study of auditory risk at the position of a bystander near a recreational firearm shooter.

Recordings of impulses from 15 recreational firearms were obtained 1 m to the left of the shooter outdoors away from reflective surfaces. Recordings were made using a pressure-calibrated 1/4 inch measurement microphone and digitally sampled at 195 kHz (24 bit depth). The acoustic characteristics of these impulses were examined, and auditory risk estimates were obtained using three contemporary damage-risk criteria (DRCs) for unprotected listeners.

Instantaneous peak levels at the bystander location ranged between 149 and 167 dB SPL, and 8 hr equivalent continuous levels (LeqA8) ranged between 64 and 83 dB SPL. Poor agreement was obtained across the three DRCs, and the DRC that was most conservative varied with the firearm. The most conservative DRC for each firearm permitted no unprotected exposures to most rifle impulses and fewer than 10 exposures to impulses from most shotguns and the single handgun included in this study. More unprotected exposures were permitted for the guns with smaller cartridges and longer barrel length.

None of the recreational firearms included in this study produced sound levels that would be considered safe for all unprotected listeners. The DRCs revealed that only a few of the small-caliber rifles and the smaller-gauge shotguns permitted more than a few shots for the average unprotected listener. This finding is important for professionals involved in hearing health care and the shooting sports because laypersons are likely to consider the bystander location to be inherently less risky because it is farther from the gun than the shooter.