Identifying vowels in CVC syllables: effects of inserting silence and noise.

Abstract

Listeners were asked to identify natural vowels in /d_d/ context under various deletion conditions. Deletion intervals, which were centered about the syllable midpoint, ranged from 60% to 90% of the syllable duration and contained either silence or broadband noise. In one condition, the three syllable types were /did/, /ded/, and /dud/; in the other condition, the three syllable types were /did/, /ded/, and/dAdV. Identification performance in the 60% and 70% deletion conditions was not substantially worse than for full syllables. Even the 90% deletion conditions yielded performance well above chance, indicating that significant coarticulatory information for vowels is contained in the first and last 10 or 15 msec of the syllable. For the short-vowel stimuli (/did/, /d∈d/, and /dλV) in the 90% deletion condition, a series of discriminant analyses were performed to assess the relative contribution of several acoustic variables to the statistical separation of the vowel categories. Several different combinations of acoustic variables (including formant frequencies at particular temporal locations and formant frequency differences over time) were sufficient to yield significant separation of the three vowel categories. However, in general, the performance of the discriminant classification program correlated only weakly with the identification performance of the listeners.