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Spatial hearing plays an important role in daily communication and orientation, but it can be affected by using hearing aids [1]. Besides non-linear signal processing, processing delay and acoustic coupling of hearing aids may disrupt the binaural and spectral cues essential for spatial hearing. To investigate their effect on localization performance, we implemented a previously proposed audiovisual search paradigm [2] using a spherical 65-loudspeaker array. Participants were asked to determine the direction of a non-intelligible speech signal by identifying the visual cue displayed on the target speaker. First, we measured the time participants required to locate the target loudspeaker, both in quiet anechoic and in a simulated cafeteria background. During this experiment, we examined their head movements, recorded with a head tracker, to gain insight into search patterns and potential confusions. In addition, we assessed how the hearing aids affected direction-dependent sound transmission, measured with a Head and Torso Simulator. Twelve adults with mild-to-moderate hearing loss and twelve adults with normal hearing participated. Both groups were tested unaided and with experimental hearing aids that allowed systematic manipulation of acoustic coupling and processing delay. Results showed that hearing aids had a general negative effect on localization performance, and overall results were better in the quiet environment. In total, normal-hearing participants had better localization performance than hearing-impaired participants. Processing delay and acoustic coupling showed no significant effects across the tested parameter conditions.

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