2025 NHCA Annual Conference

Level-dependent hearing protectors enable to perceive or even amplify soft to medium-level sounds, while protecting the ear against damaging high-level signals. This study investigates the effect of two level-dependent hearing protection devices on localization performance with two different warnings signals in noise. In a listening test with 16 normal-hearing subjects inside a horizontal array of 48 loudspeakers, localization performance dropped using earmuffs. In the most extreme cases, signals where perceived as coming from the opposite direction.
In addition, the stimuli used in the experiment were recorded with an artificial head in the same measurement setup to calculate the corresponding interaural cues. The technical measurements support the findings of the hearing study by revealing large changes of interaural level differences with earmuffs compared to open ears that were mostly in line with the subjects’ response. Finally, current localization models were run with the recordings to check their performance and predictions with the tested warning signals.
These findings indicate that it is critical to test electronic hearing protectors on changed interaural cues to avoid safety risks due to impaired localization. In addition, measurements of these cues can help predicting the perceived sound direction by human listeners, e.g., by modelling the possible outcomes.

Learning Objectives:
1. Describe possible safety risks of level-dependent hearing protectors.
2. Recall at least two ways to analyze the localization performance in listening tests.
3. Discuss the limitations of current sound localization models.