Wed-2-1-2 Enhancing the Interaural Time Difference of Bilateral Cochlear Implants with the Temporal Limits Encoder

Abstract: Normal hearing listeners mainly use interaural time differences (ITDs) and interaural level differences (ILDs) to localize sound sources in the horizontal plane. Listeners with bilateral cochlear implants (CIs), however, are with poor sensitivity to ITDs. This defect significantly limits their spatial hearing capabilities. Most CI signal processing strategies, such as the continuous interleaved sampling (CIS) strategy, are temporal-envelope-based, whereas the temporal fine structure (TFS), which contains useful cues for ITDs, is discarded. Recently, a temporal limits encoder (TLE) strategy was proposed to implicitly introduce the TFS while preserving the temporal envelope. It has demonstrated benefits in unilateral CI simulations in tasks including speech-in-noise understanding and pitch perception. This study investigates whether the ITD cues could be enhanced by a bilateral TLE strategy. Identification of five ITDs respectively associated with five sound source directions was tested with vocoded speech stimuli to compare the performance of the bilateral TLE and CIS strategies. Results show that the bilateral TLE has significantly better performance than the bilateral CIS. This finding implies that the bilateral TLE is promising in providing enhanced ITD cues for bilateral CI users. Index Terms: sound source localization, interaural time difference, bilateral cochlear implants, temporal fine structure