Psychophysical pitch biases related to vowel quality, intensity difference, and sequential order

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Abstract
Based on the analysis of the variation of the subjective equality of pitch in human subjects'' responses, a multivariate interaction model was proposed and used to demonstrate the existence of 2 types of psychophysical pitch bias. The 1st pitch bias related to a vowel acoustical characteristic was due to the vowel quality difference as a pitch difference at equal fundamental frequency. By using /a/ [the low vowel] as a common reference, this bias for 3 test vowels /e [high front vowel], i [mid vowel] u/ [high back vowel] was lower than /a/ by values of 0.54, 1.25 and 2.80 Hz, respectively. The other pitch bias related to acoustical characteristic was due to the vowel intensity difference. With intensity difference ranges from 0-30 dB, the pitch shift (bias) did not exceed 0.2 Hz at a test Fo [initial frequency] 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 was 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 3 acoustical parameters varing simultaneously was 1.5%, about 3 .times. greater than the previously reported 0.5% DL [difference limen] when Fo varied alone. The psychophysical bias of vowel was dependent upon the power spectrum and negatively correlated to the magnitude of the Fo production discrepancies of the average vowel sounds.

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