Testing the contribution of spectral cues on pitch strength judgments in normal-hearing listeners

When a wideband harmonic tone complex (wHTC) is passed through a noise vocoder, the resulting sounds can have harmonic structures with large peak-to-valley ratios in the spectra, but little or no periodicity strength in the autocorrelation functions. Noise-vocoded wHTCs evoke simultaneous noise percepts and pitch percepts similar to those evoked by iterated rippled noises. We have previously shown that spectral cues do not appear to control behavioral responses of chinchillas to noise-vocoded wHTCs in a stimulus generalization task, but do appear to contribute to pitch strength judgments in normal-hearing listeners for noise-vocoded wHTCs relative to non-vocoded wHTCs. To further test the role of spectral cues, normal-hearing listeners judged the pitch strengths of noise-vocoded wHTCs relative to infinitely-iterated rippled noise (IIRN). Stimuli had harmonic structures with a fixed fundamental frequency of 500 Hz and were presented monaurally at 50 dB SL. Listeners’ judgments of pitch strength evoked by vocoded wHTCs were generally consistent with peak-to-valley ratios of the stimuli. In order to reduce spectral cues and resolvability, stimuli were high-passed filtered. Pitch strength judgments of vocoded wHTCs were reduced following high-pass filtering. These findings suggest that spectral cues do contribute to pitch perception in human listeners.