A pitch perception study for a cochlear implant user with residual hearing in the contralateral ear

Abstract

In order to combine electrical and acoustic signals for multichannel cochlear implant users with residual hearing in the unimplanted ear, it is important to determine the degree of overlap in pitch sensations on the two sides. A pitch scaling experiment was performed maintaining constant and identical repetition rates on both the implanted (left) and normal (right) ear. The acoustic signals consisted of bandpass‐filtered pulses {with center frequencies ranging from 350–850 Hz). These were transmitted in synchrony with electrical pulses to one of five selected bipolar electrode pairs spanning 15.75 mm of the scala tympani (from approximately 2.25 to 18 mm beyond the base). The spacing between the two electrodes of each bipolar pair was 1.5 min. The experiment was repeated for repetition rates of 112.5 and 205 Hz. Pitch sensations on the left (electrical) side were reported to be as low as, and at times even lower than, on the right (acoustic) side. All signals were sealed with respect to an acoustic reference stimulus that had a bandpass filter center frequency at 450 Hz. Synthetic vowels were derived from the pitch scaling results and acoustic strategies only as well as combined electrical and acoustic strategies were tested. It was found that the best results were obtained from a combined electrical and acoustic strategy where the electrode information is chosen such that pitch perception overlap with the acoustic side is minimized. [Work supported by NIH Grant NS21027.]