Promoting off-axis listening and preserving spatial cues with Binaural Directionality II

Hearing in complex acoustic scenes is a challenge for hearing-impaired persons that often persists after amplification is applied even when fitted bilaterally. From a hearing aid (HA) processing point of view there can be several reasons for this. First, directional filters in a symmetric fitting can help increase signal-to-noise ratio for on-axis signals-of-interest. However, they also can render off-axis signals inaudible. Second, HA microphone location can degrade spatial cues that are important for localization and thus listening in complex acoustic scenes. Third, amplification itself, when applied independently at both ears, can affect spatial cues, mainly interaural-level-differences. Finally, changing acoustic scenes might require changing processing. In order to overcome some of these challenges we propose a bilateral fitting scheme that can be symmetric or asymmetric depending on the acoustic scene. The respective HA processing modes can be (a) omnidirectional, (b) directional, or (c) directional with preservation of spatial cues. In this study it was shown that asymmetric fitting helps improve off-axis audibility when prioritized while it provides natural sound and decreases listening effort for symmetric fitting in situations when audibility is not the main focus.