Effects of active and passive hearing protective devices on sound source localization, tone detection, and speech recognition

Abstract

Hearing protective devices (HPDs) such as earplugs and earmuffs offer to mitigate noise exposure and thus noise-induced hearing loss among persons frequently exposed to intense sound, e.g., military personnel or industrial workers. However, distortions of spatial acoustic information and attenuation of low-intensity sounds caused by many existing HPDs can make their use untenable in high-risk environments where auditory situational awareness is imperative. Here, we assessed (1) sound source localization accuracy using a head-turning paradigm, (2) tone detection thresholds using a two-alternative forced-choice task, and (3) speech-in-noise recognition using a modified version of the QuickSIN test in 10 young normal-hearing males wearing four different HPDs (two active, two passive), including two new and previously untested devices. Relative to unoccluded (control) performance, all tested HPDs significantly degraded performance across tasks, although one active HPD slightly improved high-frequency tone detection thresholds, and did not degrade speech recognition. Behavioral data were examined with respect to binaural acoustic information (directional transfer functions) measured in a binaural manikin with and without tested HPDs. Data reinforce previous reports that HPDs significantly compromise auditory perceptual facilities, particularly sound localization due to distortions of high-frequency pinna cues.