Evaluation of cues for horizontal-plane localization with bilateral cochlear implants

Over the past decade, cochlear implants (CIs) have become a widely accepted alternative for treatment of people with severe to profound hearing loss. Now, bilateral implantation is offered to a growing number of individuals in order to provide bene ts of binaural hearing. One of these bene ts is the ability to localize sound sources. Current CIs are not able to fully transmit the spectro-temporal information that is available for normal-hearing listeners. Experiments have shown however, that even in the absence of the ne temporal structures, CI-users are able to localize sounds in the horizontal-plane to some extent. We present a simulation study dealing with possible causes of the limited localization capabilities of CI-subjects. Concentrating on the most commonly used strategy, advanced combination encoder (ACE), we elaborate on the effects of left-right device asynchrony and that of changing the pulse rate and the number of selected spectral bands. We simulate the CI-processing up to the actuation of the electrodes complemented with a model of current spreading in the endolymph. Relying on this data, we verify localization possibilities based on interaural time differences using a generalized cross-correlation method.