ASA 124th Meeting New Orleans 1992 October

4aSP12. Perceptual boundaries of diphthong-like stimuli.

Zbigniew Czyzewski

Anna K. Nabelek

Hilary Crowley

Dept. of Audiol. and Speech Pathol., Univ. of Tennessee, Knoxville, TN 37996-0740

Fourteen-step /ai-a/ continua were generated to investigate effects of: (1) listening conditions (quiet, noise, reverberation), (2) subjects' hearing (normal and impaired), and (3) position of the end point of F1 and F2 trajectories (target frequencies). Two models of formant trajectories were tested: (1) the model proposed by Gay [J. Acoust. Soc. Am. 44, 1570--1573 (1968)] in which a characteristic and invariant rate of change in formant trajectories is required for diphthong perception and (2) the model proposed by Bladon [Speech Commun. 4, 145--154 (1984)], in which a certain change between the steady state and the target frequency is required for diphthong identification. The variable in this experiment was the length of the steady state of F1 and F2. Stimuli were generated with the Klatt synthesizer. Speech-spectrum noise was mixed at S/N=0 dB. Reverberation was generated by a computer program (T=1.1 s). Subjects, ten normal hearing and ten hearing impaired, were tested individually. Listening condition, especially reverberation, and type of formant trajectories had a significant effect on location of the boundary for both groups of subjects. Diphthongization was preserved better in the stimuli generated according to the Bladon's model than according to the Gay's model in all listening conditions. [Work supported by NIDCD.]