Identification of children's and adults' vowels: intrinsic fundamental frequency, fundamental frequency dynamics, and presence of voicing

Abstract

Three experiments investigated the role of fundamental frequency (F0) in the perception of vowels produced by children and adults. The stimuli were based on a set of American English vowels recorded in /hVd/ syllables by three groups of children (ages 3, 5, and 7 yr) and adult males and females. Experiment 1 presented natural and synthesized vowels to adult listeners for identification. To determine whether vowel-specific differences inF0 (intrinsic F0) contribute to the accuracy of vowel identification, listeners identified stimuli in which F0was held constant at the mean value across the entire vowel set for a given talker. These manipulations had no effect on identification accuracy, either when F0conditions varied from trial to trial (Experiment 1) or were blocked within a set of trials (Experiment 2). Holding F0constant over the duration of the vowel did not lower accuracy, suggesting that time-varying changes in F0make little contribution to vowel identification. Experiment 3 assessed whether the presence of F0per se provides benefits for vowel identification. This was achieved by replacing the pulsed excitation source of the synthesized voiced vowels with white noise to simulate whispered speech. Identification accuracy was lower for noise-excited than pulse-excited vowels for all talker groups. Differences between noise-excited and voiced vowels were larger for adult males than for children, suggesting that the benefits ofF0 are not due simply to improved specification of the spectrum envelope. Taken together, the results suggest that (1) F0plays a small but complex role in vowel identification in isolated words; (2) the periodicity or harmonicity contributed by F0carries more perceptual weight than either vowel-inherentF0 dynamics or a vowel's intrinsic F0, and (3) F0characteristics (dynamic patterns and intrinsic F0) provide a relatively small contribution to the reduced intelligibility commonly noted for children's vowels.