This study investigates two types of psychophysical pitch bias, one related to vowel acoustical characteristics and the other to sequential order. Based on the analysis of the variation of the subjective equality of pitch in subjects' responses, a multivariate interaction model is used to explain the experimental results and also to demonstrate the existence of the two types of psychophysical pitch bias. The first pitch bias related to a vowel acoustical characteristic is due to the vowel quality difference as a pitch difference at equal fundamental frequency. By using /a/ as a common reference, this bias for three test vowels /e, i, u/ is found to be lower than /a/ by values of 0.54 1.25, and 2,80 Hz, respectively. The other pitch bias related to acoustical characteristic is due to the vowel intensity difference. With intensity difference ranges from 0 to 30 dB, the pitch shift (bias) does not exceed 0.2 Hz at a test F0 of 100 Hz. Apparently, an intensity difference produces insignificant pitch shift in vowel sounds. The pitch bias related to the sequential order of stimuli presentation is a --0.33-Hz bias, i.e., a trend of overestimating the pitch of the second sound in temporal pitch comparison. The pitch discriminability, i.e., the just noticeable difference (JND) at 75% threshold, in an environment with three acoustical parameters varing simultaneously is found to be 1.5%, about three times greater than the previously reported 0.5% DL when F0 varies alone. Finally, the psychophysical bias of vowel is also found to depend upon the power spectrum and negatively correlated to the magnitude of the F0 production discrepancies of the average vowel sounds.

Monosyllabic, bisyllabic, and trisyllabic words of various phonemic constitutions were spoken with the four tones of standard colloqual Chinese by three speakers, two male and a female, born in Formosa, and the typical pitch patterns of the four tones for each speaker were extracted from these speech samples. Effects of the position of the syllable and the context of the kind of tone in a word on the average pitch frequency, range of change in pitch frequency, and duration of the typical pitch patterns were also analyzed. Then, the listening test was conducted to identify the kind of tone of the speech samples, and perceptual cues of the four tones were investigated through the confusion among tones, which was characteristic of each of native and nonnative listeners groups and each of nonsense and meaningful words groups. Based on the results of the acoustical analysis and the listening test, a set of essential features of the four tones were derived, and a generative model of pitch pattern of the tone accent was proposed. The results were examined utilizing listening test with the synthetic speech generated by the model. Effect of intensity pattern on the tone accent was also discussed.

This paper reports on tone perception by Chinese and American subjects and presents evidence that tones are perceived categorically by tone language speakers. Subjects were asked to identify and discriminate (ABX) synthetic speech stimuli which varied in acoustically equal steps through a range sufficient to produce the Mandarin “rising” and “level” tones. Chinese subjects showed a categorical boundary located near the middle of the stimulus space, i.e., there is a good correspondence between the crossover points in the identification functions and the peaks in the discrimination functions. American subjects exhibited a boundary closer to the level tone; this may be due to perception in a psychophysical mode. When tested on nonspeech stimuli having the same F0 characteristics, Chinese subjects showed a similar categorical boundary. Trained Chinese subjects having comparatively small JND for tones tend to perceive the stimuli only psychophysically. It would be of interest to determine if the acoustical distance between stimuli is sufficiently decreased for the discrimination task, and whether these subjects would also show a more prominent peak in their discrimination functions indicating categorical perception for tone. [Work supported by NSF, Grant no. SOC-05798A01.]

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The inferior-superior displacement of the mandible and tongue were measured photoelectrically (Chuang and Wang, ASA 58.1) during isolated production of [i.e., u, o, and ɑ]. Correlations were calculated between tongue elevation (measured with a mandibular reference) and jaw elevation as an index of their compensatory coordination. Variability of tongue and jaw positioning was obtained as a measure of articulatory precision. The correlations for high and midvowels consistently revealed moderate-to-high negative values, while the low vowels did not show this trend as clearly. The tongue height variation was found to be extremely small for high and midvowels with 0.7-mm deviation on the average, with seven subjects, while the low and back vowels produced variation three to five times greater. With devocalized vowel gestures the correlation and variability values were essentially unchanged. One interpretation of these results was that tongue-hard palate contact provides an external spatial reference for control of high-vowel tongue and jaw positioning, while no such reference is available for low-vowel production. That is, the compensatory control of tongue and jaw movements. or motor equivalence, may be dependent upon receptors in addition to intrinsic muscle receptors for high vowels. This interpretation would be consistent with the lip and jaw coordination reported for consonant articulation. [Work supported by NIH grant NS 13274.]