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Durations of acoustic segments under synchronous and delayed feedback conditions Jeffrey, Ingrid

Abstract

The present study investigates durations of acoustic segments under synchronous and delayed feedback conditions. Three subjects read a passage and four sentences at their normal rate (NORMAL), at a slow rate (SLOW SAF) under synchronous feedback, and then at a slow rate (SLOW DAF) and at a maximally fast rate (FAST DAF) under delayed auditory feedback. The delay used was determined for each subject so it would produce maximum speech disturbance. The hypotheses under test, on the basis of a pilot study were: (a) that under SLOW SAF and under delayed feedback, vowels would be prolonged proportionately more than consonants, and that continuants would be prolonged proportionately more than obstruents; and (b) that close vowels would be prolonged more under SLOW SAF and open vowels more under DAF conditions. Position in the syllable was expected to affect selectively increases in duration under DAF. The results, based on normalized data, confirmed that vowels were proportionately more prolonged than consonants under SLOW SAF and DAF conditions. Continuant consonants were proportionately more prolonged than obstruents under DAF conditions but not consistently under SLOW SAF. For the obstruents prevocalic closure was consistently more prolonged under DAF than under SLOW SAF. The hypothesis that close vowels would be prolonged more under SLOW SAF and open vowels more under DAF was not in general confirmed. The study further indicated that position in the syllable not only affected durations of segments under DAF but also under SLOW SAF: Under SLOW SAF consonants in postvocalic position were proportionately more prolonged and under DAF consonants in prevocalic position were proportionately more prolonged. It was also found that the durations of vowels in words such as function words increased proportionately more than the duration of vowels in other words and that the duration of the vowel /u/ increased proportionately more than that of open vowels. Moreover, /u/ occurred more frequently than other vowels in phonetic environments in which vowels are normally of longer duration. Finally, it is hypothesized that the syllable is a monitored unit under DAF and that the reflex level is involved in the DAF-induced speech disturbances.

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