Level-dependent hearing protectors enable listeners to perceive soft to medium-level sounds, while protecting the ear against hazardous high-level signals. The impact of these devices on localization ability due to changes in interaural cues is mostly unknown. This study investigated the influence of two hearing protectors (earplug and earmuff) in passive and one active setting on localizing two common alarm signals in noise at two signal levels compared to open ears. A listening test with 16 normal-hearing participants was conducted inside a horizontal array of 48 loudspeakers. Additionally, the stimuli were recorded with an artificial head in the same setup to calculate the corresponding occurring interaural cues. The results showed that especially one of the devices under test altered the perception of target direction, even causing alarms from one side to be misperceived as coming from the opposite side of the head. The technical measurements support these findings by revealing large changes of interaural level differences with this device compared to open ears, mostly aligning with participant responses. These findings indicate the need to test electronic hearing protectors regarding altered interaural cues to avoid safety risks due to impaired localization. Moreover, measurements of these cues can help predicting the perceived sound direction by human listeners.
Buchholz et al. (Thu,) studied this question.