Development of an electromechanical test system and acoustical metrics to predict impacts of hearing protection devices on sound localization

Abstract

Hearing protection devices (HPDs) such as earplugs and earmuffs can protect users from dangerously high acoustical pressures but also distort cues important for the spatial localization of sounds, likely through spectral distortions associated with occlusion of the pinnae. Evaluation of the degree to which an HPD distorts localization cues is essential for critical situations where users must be protected from high pressures but maintain spatial awareness. Automated testing offers several prospective advantages over human subject testing including cost, speed, and repeatability. In this paper, we describe an electromechanical system using a rotating manikin test fixture and a speaker on a track to simulate a hemispheric speaker array. The sound source localization impact of an HPD is estimated by comparing test signals recorded by the manikin with and without an HPD in place. Test results, as a function of sound source azimuth and elevation in the virtual speaker array, and as an average across locations, are shown for a variety of HPDs. Results are compared to an initial set of parallel measurements of sound localization during HPD use in human subjects.