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

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.

A critical review of the literature on comfort of hearing protection devices: definition of comfort and identification of its main attributes for earplug types

“…Indeed, in the case of hearing aids, the sound quality is one of the most important factors to overall satisfaction and (dis)comfort is partly or completely characterized by acoustical attributes such as the "occlusion effect" and "acoustic feedback" (Branda 2012;French-Saint George and Barr-Hamilton 1978;Furstenberg, Gordon, and Baccaro 1988;Mackenzie, Browning, and McClymont 1989). In the same way, acoustical attributes are included in the construct of comfort in studies dealing with hearing protectors dedicated to musicians (Bernier 2013) or workers for which spatial acoustic information is of upmost importance and should not be altered (e.g., military or law enforcement) (Brown et al 2015;Ribera et al 1995).…”

Autonomic responses to blast overpressure can be elicited by exclusively exposing the ear in rats

“…Soldiers frequently wear little or no ear protection, citing a necessity for situational awareness through unhindered sound localization (Abel, 2008, Brown et al., 2015, Clasing and Casali, 2014, Jones and Pearson, 2016). If the hypotension induced in our rats by high-intensity blast via the ear canal also occurs in humans, it would likely induce syncope, preventing an individual's ability to react to threats, seek safety or help, or treat themselves until help arrives.…”

“…The advanced combat helmet, the current helmet of the U.S. Army, uses layers of Kevlar and a foam suspension to protect the skull from penetrating and blunt-force injuries, but leaves the ears, eyes, nose, and mouth all exposed to the surrounding air, permitting pressure from a blast to interact (Meaney et al., 2014, Moore et al., 2009). Nonetheless, soldiers frequently wear little to no ear protection, citing a necessity for situational awareness through unhindered sound localization (Abel, 2008, Brown et al., 2015, Clasing and Casali, 2014, Jones and Pearson, 2016). A perforated eardrum is the most frequently reported blast injury (Cernak and Noble-Haeusslein, 2010, Choi, 2012, Darley and Kellman, 2010, DePalma et al., 2005, Gan et al., 2016, Garth, 1994, Helling, 2004, Katz et al., 1989, Kronenberg et al., 1993, Mayorga, 1997, Patterson and Hamernik, 1997, Phillips, 1986).…”

Living and Working in a Multisensory World: From Basic Neuroscience to the Hospital

“…As a result, the patients can experience normal hearing without the negative consequences of aversive alarms. By globally decrease acoustic input, these in-ear devices may contribute to a decrease in PICS and ICU delirium [125,126].…”