Interactions between Pitch and Timbre Perception in Normal-hearing Listeners and Cochlear Implant Users

Pitch and timbre perception are two important dimensions of auditory perception. These aspects of sound aid the understanding of our environment, and contribute to normal everyday functioning. It is therefore important to determine the nature of perceptual interaction between these two dimensions of sound. This study tested the interactions between pitch perception associated with the fundamental frequency (F0) and sharpness perception associated with the spectral slope of harmonic complex tones in normal hearing (NH) listeners and cochlear implant (CI) users. Pitch and sharpness ranking was measured without changes in the non-target dimension (Experiment 1), with different amounts of unrelated changes in the non-target dimension (Experiment 2), and with congruent/incongruent changes of similar perceptual salience in the non-target dimension (Experiment 3). The results showed that CI users had significantly worse pitch and sharpness ranking thresholds than NH listeners. Pitch and sharpness perception had symmetric interactions in NH listeners. However, for CI users, spectral slope changes significantly affected pitch ranking, while F0 changes had no significant effect on sharpness ranking. CI users' pitch ranking sensitivity was significantly better with congruent than with incongruent spectral slope changes. These results have important implications for CI processing strategies to better transmit pitch and timbre cues to CI users.