Azimuthal auditory localization of gunshots in a realistic field environment: Effects of open-ear versus hearing protection-enhancement devices (HPEDs), military vehicle noise, and hearing impairment

Abstract

Objective: A controlled field experiment was conducted to evaluate localization of suprathreshold gunshot reports (from blank cartridges) with four hearing protection-enhancement devices (HPEDs) in comparison to the open ear with ambient outdoor noise and in 82 dBA diesel military heavy truck noise. Design: Five measures of localization accuracy and response time for eight shooter positions in azimuth were measured. Study sample: Nine normal-hearing and four impaired-hearing participants were tested. Results: Statistical analysis showed worse accuracy and response time performance with the electronic earmuffs (Peltor Com-Tac II™ in full gain position) than with the other tested HPEDs (Etymotic EB 1 and EB 15 High-Fidelity Electronic BlastPLG™ electronic earplugs, both set to Lo gain positions; and 3M Single-Ended Combat Arms™ passive earplug in level-dependent, “open” position). Performance with all HPEDs was worse than that with the open ear, except on right-left confusions, in which the earmuff stood alone as worst, and in response time, for which the EB 1 was equivalent to the open ear. There was no significant main effect of noise on performance. Hearing impairment increased right-left confusions. Subjective ratings related to localization generally corroborated objective localization performance. Conclusions: None of the tested HPEDs preserved “normal” localization performance.

Key Words::

• Hearing protection-enhancement device
• electronic hearing protector
• level dependent hearing protector
• sound localization
• impulse noise localization
• localization in noise
• firearm noise
• gunshot
• sniper
• auditory localization
• azimuth

Acknowledgements

This research was presented at the National Hearing Conservation Association Conference in Mesa, Arizona, USA, February 24–26, 2011. Research funding was provided by Etymotic Research, Inc., who had no influence over experimental protocols or analyses of data. The first author was supported on a Department of Defense SMART doctoral scholarship during her Ph.D. program. The conclusions herein are those of the authors, and are not intended to represent the position of Virginia Tech or Etymotic Research, Inc. The study was approved by the Virginia Tech Institutional Review Board for human subjects use.

Declaration of interest: The fourth author (MK) has a financial interest in Etymotic Research. The other authors report no conflict of interest. The authors alone are responsible for the content and writing of the paper.