Vowel boundaries for steady-state and transient formants.

Abstract

Fifteen-step /i–eh/ continua were generated to investigate effects of: (1) listening conditions (quiet, noise, and reverberation), (2) subjects’ hearing (normal and impaired), and (3) trajectories of F1 and F2 (all steady-state, F1 changing in upward or downward direction, and both F1 and F2 changing in upward or downward direction). Stimuli (each repeated 10 times) generated with the Klatt synthesizer were 200 ms long. Speech-spectrum noise was mixed at S/N=0 dB. Reverberation was generated by a computer program and convolved with the stimuli (T=0.9 s). Subjects, 10 in each group, were tested individually. Stimuli were delivered monaurally through an earphone at a comfortable level. Listening condition had no effect on the boundary location for either group of subjects and had no effect on boundary slope for the normal-hearing subjects but a significant effect on slope for hearing-impaired subjects. Type of trajectories had a significant effect on location of the boundary only for the hearing-impaired subjects and on boundary slope for both groups of subjects; the two continua with F1 and with F1 and F2 changing in downward direction produced different results than the continua with steady-state formants and with formants in upward direction. [Work supported by NIDCD.]