Effects of Active and Passive Hearing Protection Devices on Sound Source Localization, Speech Recognition, and Tone Detection

TLDR

Hearing protection devices mitigate noise exposure but distort spatial cues and reduce low‑intensity audibility, jeopardizing situational awareness in high‑risk settings such as military or law enforcement. The study aimed to evaluate how four HPDs—two active and two passive—affect sound source localization, speech‑in‑noise recognition, and tone detection thresholds. Ten young normal‑hearing male participants performed head‑turning, QuickSIN, and two‑alternative forced‑choice tasks while wearing the HPDs, and their responses were compared to head‑related transfer functions measured with a binaural manikin with and without the devices. All HPDs significantly impaired performance relative to the unoccluded condition, though one active device slightly improved high‑frequency tone detection and preserved speech recognition, confirming that HPDs compromise auditory perception—especially localization due to high‑frequency spectral cue distortion and front‑back confusion.

Abstract

Hearing protection devices (HPDs) such as earplugs offer to mitigate noise exposure and reduce the incidence of hearing loss among persons frequently exposed to intense sound. However, distortions of spatial acoustic information and reduced audibility of low-intensity sounds caused by many existing HPDs can make their use untenable in high-risk (e.g., military or law enforcement) environments where auditory situational awareness is imperative. Here we assessed (1) sound source localization accuracy using a head-turning paradigm, (2) speech-in-noise recognition using a modified version of the QuickSIN test, and (3) tone detection thresholds using a two-alternative forced-choice task. Subjects were 10 young normal-hearing males. Four different HPDs were tested (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 head-related transfer functions measured using a binaural manikin with and without tested HPDs in place. Data reinforce previous reports that HPDs significantly compromise a variety of auditory perceptual facilities, particularly sound localization due to distortions of high-frequency spectral cues that are important for the avoidance of front-back confusions.