ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

3aSP18. The effects of duration changes on the perception of vowel sequences.

Magdalene H. Chalikia

Tammy Dresser

Dept. of Psychol., Moorhead State Univ., Moorhead, MN 56563)

Previous studies have shown that listeners exposed to a repeated sequence of steady-state vowels of same duration and pitch) experience phonemic transformations, and report hearing words and phrases absent in the original stimulus. A previous study [M. H. Chalikia, R. Meyer, and R. Lindemann, 34th Psychon. Society Meet. 1993)] investigated the possible effects of variations in vowel duration. Duration variations ranged from 30 to 120 ms per vowel. Listeners successfully matched these stimuli to the verbal forms heard with vowels of equal duration and pitch, confirming the robust, stable nature of the verbal organizations. It was suggested that these organizations are based upon objective acoustic characteristics, and the stimulus manipulations were probably perceived as prosodic variations. In this study a broader variation in duration was employed 10--300 ms), in an attempt to examine listeners' limitations in performing the matching task. Six base-line sequences of six 80-ms vowels at 100 Hz), followed by a 300-ms silent gap, were used. Four variations of these were created by randomly changing the duration of individual vowels within a sequence. Most listeners were not able to perform the task. Implications concerning the perceptual organization of speech will be discussed.