Interleaved Processors Improve Cochlear Implant Patients' Spectral Resolution

Abstract

Objective: Cochlear implant patients have difficulty in noisy environments, in part, because of channel interaction. Interleaving the signal by sending every other channel to the opposite ear has the potential to reduce channel interaction by increasing the space between channels in each ear. Interleaving still potentially provides the same amount of spectral information when the two ears are combined. Although this method has been successful in other populations such as hearing aid users, interleaving with cochlear implant patients has not yielded consistent benefits. This may be because perceptual misalignment between the two ears, and the spacing between stimulation locations must be taken into account before interleaving.

Design: Eight bilateral cochlear implant users were tested. After perceptually aligning the two ears, 12-channel maps were made that spanned the entire aligned portions of the array. Interleaved maps were created by removing every other channel from each ear. Participants' spectral resolution and localization abilities were measured with perceptually aligned processing strategies both with and without interleaving.

Results: There was a significant improvement in spectral resolution with interleaving. However, there was no significant effect of interleaving on localization abilities.

Conclusions: The results indicate that interleaving can improve cochlear implant users' spectral resolution. However, it may be necessary to perceptually align the two ears and/or use relatively large spacing between stimulation locations.

Figure 1

Spectral resolution was significantly better with interleaved processors. Each data point indicates results for one subject, labeled by the subjects' ID. Points above the diagonal line indicate that performance is better with the interleaved processors. Points below the diagonal line indicate that performance is better with the non-interleaved processors.

Figure 2

There was no significant difference between localization performance with interleaved and non-interleaved processors. Each data point indicates results for one subject, labeled by the subjects' ID. Points above the diagonal line indicate that performance is better with the interleaved processors. Points below the diagonal line indicate that performance is better with the non-interleaved processors.