Pitch perception of harmonic complex tones based on excitation patterns

Fundamental frequency difference limens were measured to study whether pitch perception of medium-rank harmonic complex tones depends on the resolvability of the compo- nents and to study the effect of masker tone on discrimination performance. Target tone was presented alone, or mixed with the masker, which were filtered into the same bandpass frequency region （low, medium, or high） to obtain different resolvability. There were five kinds of funda- mental frequency difference and four kinds of phase combination between target and masker. Five young subjects participated in experiments, all of whom had normal hearing （thresholds ≤ 15 dB HL）. Results found fundamental frequency difference limens were increased with up-shift frequency region of the harmonics. The fundamental frequency difference between target and masker had a significant impact on the performance, while phase effects were small. Analysis suggested that resolvability of harmonics had a significant impact on the fundamental frequency difference limens, but pitch perception of medium-rank harmonics was not based on the resolv- ability. Analysis also suggested that most results of pitch perception of target-masker mixture were closely correlated with peaks on the excitation patterns.

Excitation patterns and phonetic identities of Chinese vowels

After entering the peripheral auditory system, a sound undergoes many significant changes. The excitation pattern describes these changes psychoacoustically as inner expression. This study investigates the relations between excitation patterns and their phonetic qualities for Chinese steady-state vowels. First, the peak positions of the envelope of excitation patterns were measured on a database. The results demonstrated that each Chinese vowel has its own special position for the representative peak of the excitation pattern. Second, to examine the sufficiency of these results, a series of experiments that consisted of identification and evaluation tasks were conducted, in which spectral components of natural isolated vowels were manipulated to create certain excitation patterns. Subjects＇ responses of these stimuli show that the position of the representative peak of the excitation pattern of a vowel plays a crucial role on its phonetic identity. The results suggest that the phonetic identity of vowels is determined by the position of the representative peak of the excitation pattern evoked by it, and other peaks, if any, do not have phonetic meaning. Additionally, several phenomena about speech perception are discussed on the basis of this study.