Temporal Pitch in Electric Hearing with Amplitude-Modulated Pulse Trains and Inserted Short Inter-Pulse Intervals
* Presenting author
Temporal pitch sensitivity in cochlear-implant (CI) listeners can be enhanced by inserting pulses with short inter-pulse intervals (SIPIs) in amplitude-modulated (AM) high-rate pulse trains. AM high-rate pulse trains are employed in current CI stimulation paradigms. While pitch sensitivity to AM improves with increasing modulation depth (MD), adding SIPI pulses results in uniform pitch sensitivity across MDs. When AM and SIPI pulses encode different frequencies, it is unclear which frequency dominates the pitch percept. To this end, pitch-discrimination sensitivity was measured in CI listeners with two MDs (0.1 and 0.5) and certain fundamental frequencies in the range of male and female speech. In a pitch-discrimination task, intervals were set up such that (a) both AM and SIPI frequencies changed congruently, (b) either AM or SIPI frequency remained constant, or (c) both SIPI and AM frequency changed incongruently. Discrimination performance was hypothesized to depend on AM and SIPI frequency differences (ΔAM and ΔSIPI). Statistical analysis showed that the performance was significantly accounted for by ΔSIPI and that it did not differ between MDs. This indicates that care should be taken to preserve original pitch cues provided in CI stimulation paradigms that incorporate SIPI pulses.