Pitches of concurrent vowels

Abstract

When two vowels on different fundamental frequencies (F0’s) are presented concurrently, listeners can often report which vowel has the higher pitch. However, when the duration of the vowels is brief, listeners are more likely to misidentify the vowels and/or rank their pitches incorrectly. Four experienced listeners matched the pitches evoked by pairs of concurrent vowels whose durations were either 200 or 50 ms. The reference stimuli were pairwise combinations of the vowels /i/, /a/, /u/, /æ/, and /hooked backward eh/. One F0 was 100 Hz; the other was 0, 0.25, 0.5, 1, 2, or 4 semitones higher. When the F0 difference was less than one semitone, the majority of listeners’ matches clustered around the mean of the two F0’s, and they generally reported only one pitch. With larger F0 differences, 50-ms vowels generated more variable matching histograms than 200-ms stimuli. With 200-ms stimuli, listeners were more likely to report two pitches and their matches were more often clustered around the two F0’s. However, consistent evidence of bimodality emerged only for 200-ms stimuli with the largest F0 separation of four semitones. These results indicate that the pitches of concurrent vowels emerge less clearly when the stimuli are brief. [Work supported by NIDCD.]