Ten-year longitudinal study of the effect of impulse noise exposure from gunshot on inner ear function

Abstract

This longitudinal study investigated how chronic gunshot noise exposure affects cochlear and saccular function in police officers who engaged in regular target shooting practice using dual protection (ear plugs plus earmuffs) for >10 years. In 1997, 20 male police officers underwent audiometry before and two weeks after shooting. Twelve of the original subjects were re-examined by audiometry coupled with vestibular evoked myogenic potential (VEMP) test in 2007. Significant deterioration of mean hearing thresholds at frequencies of 500 Hz through 4000 Hz was noted ten years later, affecting both ears. However, only the frequencies of 4000 and 6000 Hz on the left ear revealed significant difference in mean hearing thresholds compared with healthy controls. Abnormal VEMP responses were evident in nine police officers (75%), including absent VEMPs 7 and delayed VEMPs 2. In conclusion, deterioration to hearing may occur after long term exposure to gunshots, even when double hearing protection is used. Further study is in progress regarding how to preserve both cochlear and saccular function during long term gunshot exposure.

Inner Ear Damage by Firecracker Trauma

“…Further, a 10-year longitudinal study in police officers from a single division, who received target shooting practice monthly for > 10 years, revealed a 75% cVEMP abnormality [Wu and Young, 2009]. Although all police officers wear ear plugs combined with earmuffs to protect the cochlea, these fail to prevent vibration injury to the saccule transmitted from gunshots.…”

Noise Exposure Assessment for University Police Officers during Rifle and Shotgun Qualifications

“…This may be due in part to the fact that this study was conducted in an isolated outdoor shooting range in a remote location surrounded by dense vegetation where sound levels often had adequate space to dissipate or be absorbed. Several of the studies reviewed for comparison were conducted in indoor settings or shooting ranges (Wu and Young 2009, Murphy and Tubbs 2007, Pawlaczyk-Luszczynska et al 2004) and this may provide some explanation for the higher noise levels previously reported.…”

“…Hearing protective devices (HPDs), such as earplugs or earmuffs, have been found to be effective in reducing noise levels to prevent NIHL and can effectively attenuate the peak SPL typically by as much as 25-35 dBA (Collee et al 2011, Mrena et al 2009, Muhr and Rosenhall 2011, Pawlaczyk-Luszczynska et al 2004). In addition, doubling the HPDs by using both earplugs and earmuffs can further reduce the peak levels by an additional 15-20 dBA, resulting in over a 40 dBA reduction (Murphy andTubbs 2007, Wu andYoung 2009). Communication issues among officers, which further increases with double protection, may be solved by the use of electronic HPDs, such as electronic level limiting earmuffs (Murphy and Tubbs 2007).…”

“…The weapons used routinely by police officers such as small caliber weapons, typically emit hazardous noise levels that ranged from 140 to 160 dBA (Murphy and Tubbs 2007). Such high noise levels have the potential to cause hearing loss, which is a significant hazard in a number of populations, including military personnel, police officers, and recreational shooters (Pawlaczyk-Luszczynska et al 2004, Wu andYoung 2009). Police officers, when compared to the military, use the same or similar weapons which produce hazardous noise levels (Lindblad et al 2011, Muhr and, and also have similar requirements to maintain proficiency with various weapons (Murphy and Tubbs 2007).…”

Vestibular Hearing and Speech Processing

“…Stimulation of the vestibular system with air-conducted sound activates predominantly saccular afferents, Wu and Young [1], Curthoys et al [2], and Wang et al [3]. The auditory sensitivity of the saccule (vestibular hearing) has been demonstrated in amphibians, birds, mammals, and among human, Curthoys et al [4], Eatock and Lysakowski [5], and Zhou et al [6].…”