Binaural-Cue Reweighting in Normal-Hearing and Cochlear-Implant Listeners
* Presenting author
Abstract:
Normal-hearing (NH) listeners rely on both interaural time (ITDs) and level (ILDs) differences for azimuthal sound localization. Localization with cochlear implants (CIs), however, is mainly based on ILDs. Since current envelope-based stimulation strategies do not encode salient ITD cues, CI listeners may learn to rely on ILDs instead.To study such ITD/ILD reweighting, two experiments (NH and CI) were performed using a lateralization task with spatially inconsistent binaural cues in a virtual audio-visual environment. A multi-day training reinforcing either ITDs or ILDs was preceded and followed by a test measuring the ITD/ILD weighting. NH listeners, assigned to either a reinforced-ITD or reinforced-ILD group, lateralized narrow-band (2-4 kHz) noise bursts. For CI listeners, 100-pps and 300-pps unmodulated pulse trains were presented at a single interaurally place-matched electrode pair and only ITDs were reinforced. Additionally, CI listeners’ binaural-cue thresholds were measured before and after training.Both NH groups increased their weighting for the reinforced cue. CI listeners increased their ITD weighting for 100-pps but not for 300-pps stimuli, whereas binaural-cue thresholds did not change.The results suggest that the perceptual weighting of ITDs and ILDs can be changed, which may make ITDs better usable once they are saliently conveyed by CI systems.