Quantifying impacts of hearing protection devices on sound localization in azimuth and elevation: Toward predictors of performance

Modern hearing protection devices (HPDs) effectively mitigate the risk of noise-induced hearing loss when used as intended, and some even preserve the audibility of low-to-moderate-intensity sounds. Nonetheless, negative auditory perceptual side-effects continue to limit usability in critical settings. Most notably, dozens of studies have shown that HPDs lead to significant errors in sound source localization. Several studies have specifically linked such errors to HPD-induced distortions of the spectra of transmitted signals. Here we provide an update on a multi-site study designed to capture patterns in sound localization errors (among other impacts) across different classes of HPDs, toward validation of acoustic predictors of HPD performance. At two independent study sites, human listeners localized brief broadband signals with open ears (control) and during use of passive and active earplug and earmuff-style devices. Sources spanning 360° in azimuth and −30° to + 60° in elevation enabled measurement, via wireless head-tracking, of 2-D localization error across a broad range of source locations. New metrics integrating these measurements with acoustic data, obtained via standardized HPD test fixtures as well as in-ear microphones designed to capture individual variation in HPD impacts, will support application-specific selection of existing HPDs and inform the design of new HPDs.