Fraunhofer IDMT, HSA
Abstract:
Level-dependent hearing protectors enable to perceive soft- to medium-level sounds without processing, while protecting the
ear against hazardous high-level signals by active level attenuation. However, the level-dependent behavior can potentially affect
naturally occurring binaural cues and, hence, impair localization abilities.
This study therefore investigated the influence of two hearing protectors (earplug and earmuff), each in passive and one active
setting, on localization of reverse alarms in noise at two signal levels compared to open ears. Localization was measured in 16
normal-hearing subjects inside a horizontal array of 48 loudspeakers. Additionally, the stimuli were recorded with an artificial
head
in the same measurement setup to investigate the corresponding interaural cues.
The results showed that especially the active earmuff at the higher level led to a reversed perception of the target direction.
The
objective measurements revealed large changes of interaural level differences with earmuffs compared to open ears which
were
mostly consistent with the subjects’ responses.
These findings indicate that it is critical to test electronic hearing protectors with respect to changes in interaural cues to avoid
safety risks due to impeded localization. Results also indicate that measured interaural cues can provide an estimate of the
perceived sound direction by human listeners.