Effects of modulation wave shape on modulation frequency discrimination with electrical hearing

Abstract

Amplitude modulations of pulsitile stimulation can be used to convey pitch information to cochlear implant users. One variable in designing cochlear implant speech processors is the choice of modulation waveform used to convey pitch information. Modulation frequency discrimination thresholds were measured for 100 Hz modulations with four waveforms (sine, sawtooth, a sharpened sawtooth, and square). Just-noticeable differences (JNDs) were similar for all but the square waveform, which often produced larger JNDs. The results suggest that a sine, sawtooth, and sharpened sawtooth waveforms are likely to provide similar pitch discrimination within a speech processing strategy.

Figures

Figure 1

Illustration of the four experimental modulation waveforms.

Figure 2

(Color online) Modulation frequency JNDs (in percent difference re: 100 Hz) for individual subjects. The three panels show data for the three experimental electrode locations. The error bars show one standard error of the mean.