On the role of the fundamental frequency in vowel perception

Vowel identification tests were carried out using 200 synthesized vowel-like stimuli to examine the role of the fundamental frequency F0 in vowel perception. These stimuli were synthetic versions of the five Japanese vowels, /i/, /e/, /a/, /o/, and /u/, of which the F0 and/or the formant frequencies Fi (i = 1,2,3,4) were modified: ten F0 values were formed by adding n/3 Bark (n = 0,1,…,9) to the original F0. Four formant frequency sets were formed by adding m Bark (m = 0,1,2,3) to the original formant frequencies for each vowel. The results are the following: (1) perceived vowel height articulation shifts upward when the F0 shifts upward, while all formant frequencies remain the same: (2) this shift in vowel height is more distinct amid mid and low vowels than for high vowels; and (3) vowel height does not change when the F0 as well as all formant frequencies are shifted upward the same amount along the Bark scale. Further results, along with the hypothesis that a high F0 is regarded as the first formant in middle and low vowel perception, will be discussed.