Adapting bilateral directional processing to individual and situational influences

This study examined differences in benefit from bilateral directional processing. Groups of listeners with symmetric or asymmetric audiograms <2 kHz, a large spread in the binaural contribution to speech-in-noise reception (i.e. the binaural intelligibility level difference, BILD), and no difference in age or overall degree of hearing loss took part. Aided speech reception was measured using virtual acoustics together with a simulation of a linked pair of closed-fit behind-the-ear hearing aids. Five processing schemes and three acoustic scenarios were used. The processing schemes differed in the trade-off between signal-to-noise ratio (SNR) improvement and binaural cue preservation. The acoustic scenarios consisted of a frontal target talker and two lateral speech maskers or spatially diffuse noise. For both groups, a significant interaction between BILD, processing scheme and acoustic scenario was found. This interaction implied that, for lateral speech maskers, users with BILDs >2 dB profited more from low-frequency binaural cues than from greater SNR improvement, while for smaller BILDs the opposite was true. Audiometric asymmetry reduced the BILD influence. In spatially diffuse noise, the maximal SNR improvement was beneficial. Moreover, binaural tone-in-noise detection performance (N₀S_π threshold) at 500 Hz predicted the benefit from low-frequency binaural cues effectively. These results provide a basis for adapting bilateral directional processing to the user and the scenario.