Pitch of vowels: Experimental and theoretical investigation of its dependence on vowel quality

Abstract

The auditory pitches of the vowels /a/, /e/, /fx1-137/, /i/, /o/, /u/, /æ/, /ø/ and /y/ were measured in psychoacoustic experiments as a function of the vowels' spectral envelopes (vowel quality). The method of paired comparison (2AFC) was applied. Two fundamental frequencies (125 and 250 Hz) and three SPL's (45, 60 and 75 dB) were used. The results of 14 subjects show that the pitch of vowels varies systematically depending on vowel quality. The vowels /a/ and /æ/ evoke a higher pitch than /i/ and /y/ when the same fundamental frequency is used. The differences between /æ/ and /y/ amount to 2% on average, with 125 Hz fundamental frequency. The SPL of a vowel has only a weak influence on its pitch. The experimental results were correlated with theoretical predictions, using a pitch-extraction algorithm based on the virtual pitch theory. The small but significant pitch departures different vowels are reliably predicted by the algorithm.