Predicting the benefit of binaural cue preservation in bilateral directional processing schemes for listeners with impaired hearing

Linked pairs of hearing aids offer various possibilities for directional processing providing adjustable trade-off between improving signal-to-noise ratio and preserving binaural listening. The benefit depends on the processing scheme, the acoustic scenario, and the listener’s ability to exploit binaural cues. Neher et al. (2017) investigated candidacy for different bilateral processing schemes for 20 elderly listeners with symmetric and 19 age matched listeners with asymmetric hearing thresholds below 2 kHz. The acoustic scenarios consisted of a frontal target talker presented against two intelligible or unintelligible speech maskers from ±60° azimuth. In this study, the speech reception threshold (SRT) data were compared to predictions of the binaural speech intelligibility model (BSIM; Beutelmann et al., 2010), which was used to model pure better-ear-glimpsing as well as additional binaural unmasking. The speech intelligibility index (SII), which served as backend of BSIM, was calibrated to an individual reference value at the SRT for each listener. This reference value mirrors the amount of acoustical information needed by the listener to achieve the SRT and correlated with the listeners’ ability to process temporal fine structure. BSIM revealed a benefit due to binaural processing in well-performing listeners when processing provided low-frequency interaural timing cues.