Abstract
The ability of listeners with cochlear implants to detect amplitude modulation (AM) of stimulation level has been linked to their ability to understand speech, but the specific features of AM stimuli that enable their detection remains unknown. At low modulation rates sensitivity is strongly associated with intensity resolution, but at high modulation rates sensitivity to AM stimuli further degrades, indicating additional temporal limits on detection. The goal of this work is to identify the specific components of AM pulse trains that listeners with cochlear implants use to detect AM. We measured increment and decrement detection thresholds for multiple increment/decrement durations in these listeners and compared these thresholds to their ability to detect sinusoidal AM at different rates. Electrical stimulation also provides a unique opportunity to present arbitrary stimulation waveforms through a single electrode, so we generated additional waveforms that either sharpened or smoothed different portions of each AM period to determine how this altered detectability. Preliminary results suggest that increments in stimulation level are the critical feature that listeners use to detect AM, and that at high AM rates increments are partially masked by preceding stimulation.
Published Version
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