Pitch perception for sequences of impulse responses whose scaling alternates at every cycle.

The purpose of this study is to investigate the sufficient "similarity" between consecutive auditory events for the auditory system to define the fundamental period for pitch perception. It is possible to contaminate the periodicity of harmonic complex tones by scaling the impulse response in the time domain at every other cycle. Scale-alternating wavelet sequences (SAWS) in which two impulse responses with different scaling factors alternated were generated based on impulse responses obtained from Japanese vowels spoken by a male speaker. Preliminary listening to such signals indicated that the perceived pitch went down an octave relative to the original when the scaling factor exceeded a certain degree. In the first experiment, pitch matching was measured as a function of the scaling factor by the method of adjustment where the comparison stimuli were completely periodic with adjustable base periods. The pitch shift was discontinuous against the base period, chromatic continuum. In the second experiment, pitch matching was investigated with comparison stimuli whose odd harmonics were attenuated. This procedure provides a stimulus continuum where the pitch moved up an octave without changing its pitch chroma. The attenuation of the odd harmonics needed to match the SAWS varied systematically as a function of the degree of scaling. The relation between pitch matching and the peak height along the time interval axis of the stabilized auditory image is discussed.