Pitch effects on vowel roughness and spectral noise

The effects of vocal pitch on the perceived roughess and the acoustic spectral noise levels of two test vowels were investigated. Ten normal-speaking young adult subjects (5 male and 5 female) each produced at one intensity the high vowel /u/ and the low vowel /a/ at four test pitches. The pitches ranged, for each subject, from habitual pitch to a pitch one octave higher. Spectral noise level (SNL) measures and listener ratings of roughness were obtained for each vowel sample, and the fundamental frequency of each sample was measured. It was found that both the mean SNL and the perceived roughness of the test phonations diminished significantly (P< 0·05) when vocal pitch was raised by an octave. This finding held for the two sexes (considered separately) and for both test vowels. When the data were compared across sexes, it was found for each test vowel that the roughness ratings and the SNL means were more closely related to the relative pitch (re subjects’ habitual pitch) at which the test phonations were produced than to the absolute fundamental frequency of phonation.