Interaction Between Head Movement Behavior and Simulated Spatial Filtering: Comparing Free Conversation and Speech Tests in Virtual Reality.

The benefit provided by hearing devices often differs between laboratory evaluations and real-world conditions, due to low signal-to-noise ratio (SNR) in adaptive speech tests and differences in head movement behavior between laboratory evaluations and real conversations. This study aimed to investigate whether SNR improvement provided by a spatial filter can be measured during free conversation in virtual reality (VR) and to compare this SNR improvement with the benefit measured using a speech test with two spatially separated talkers in the same VR. Two experimental conditions were tested in 11 normal-hearing participants. Condition 1 involved free conversations between a participant and two confederates represented by avatars, and Condition 2 utilized an adaptive speech test with two speakers, presented by the same avatars. Acoustic simulations were used to render speech signals, background noise and room acoustics. A spatial filter with two levels of selectivity was simulated in VR using the participant's actual dynamic head orientation. Acoustic measures of the benefit of the spatial filter were derived from these simulated signals. The benefit was higher when measured in free conversations than in the speech test. Additionally, participants were found to move their heads closer to active speakers during free conversation than during the speech test. Furthermore, SNR in free conversations was closer to SNRs typical of conversational environments. These findings suggest that the effectiveness of hearing devices can be evaluated through conversations in VR at more realistic SNRs. Consequently, this approach may improve the ecological validity of hearing aid research outcomes.