The role of vowel quality in pitch comparison

Abstract

In normal speech, the fundamental frequency (F0) is higher for close than for open vowels. This phenomenon is called intrinsic F0 (IF0). With constant F0, open vowels sound higher pitched than close ones. Applying Hellström’s sensation weighting model for stimulus comparison, IF0 was hypothesized to contribute to this effect by making listeners’ adaptation levels (ALs) for F0 differ between vowels. Two groups of listeners (language students, choir singers) judged, for pairs of successively presented synthetic vowels, which vowel had the higher pitch. The judgments were clearly based on vowel quality; there were also large time-order effects. The results were well accounted for by the model. It is suggested that the adaptation-weighting mechanism increases the discriminability of vowels, and also equalizes the average pitch of different vowels in normal speech.