Two-dimensional sound localization during hearing protector use: Human performance and acoustic prediction

Hearing protection devices (HPDs) are essential safety equipment for workers in noisy settings, but can degrade auditory perception. For example, dozens of studies have demonstrated that HPDs disrupt sound source localization, a critical limitation for some use cases. However, a majority of studies have evaluated performance for a small sample of practiced participants, a small number of source locations, and/or a small set of HPDs, making it difficult to distill generalizable factors affecting localization performance. Here, sound localization was measured in 130 participants across two study sites. At each site, test stimuli spanned 24 source locations (eight azimuths, three elevations) in five different listening conditions: open ears (baseline), and four different HPDs. In all conditions, test stimuli were brief noise bursts; in some conditions, multiple source levels or durations were tested. Parallel acoustic measurements were completed at each site using a binaural manikin. Data suggest that HPDs may disrupt localization via at least three means: (1) attenuation can render air-conducted localization cues inaudible, (2) frequency distortion can disrupt audible monaural localization cues, and (3) asymmetric attenuation can disrupt audible binaural localization cues. However, data also evince large intersubject variability and task-dependent biases not readily captured using conventional acoustic measures.