The effects of differential vowel prolongations on perceptions of speech naturalness

Abstract

Prolongation of speech sounds is currently used to modify stuttering and enhance fluency. Prolonged speech (PS) (e.g., prolonged vowels, prolongation throughout utterances) is, however, often perceived as unnatural by listeners. This study examined at which durations and in which contexts 52 college students (primary language was American English) perceived PS to be unnatural. Stimuli were limited to controlled variation in prolongation of the vowel in the middle single-syllable word of a carrier phrase (i.e., say word again). The prolongation was effected by digital waveform manipulation within the Kay Elemetrics Computerized Speech Laboratory (CSL). The listeners judged if they strongly agreed, agreed, or disagreed that the phrases sounded natural. Results indicated that the extent of vowel duration (and possibly context) does influence listener's perception of speech naturalness, findings which can be applied to facilitate fluency therapy. Educational objectives: (1) The reader will learn about and be able to summarize the digital waveform manipulation procedure in the study. (2) The reader will learn about and be able to describe the effects of differential vowel prolongation on listener's perception of speech naturalness. (3) The reader will learn about and evaluate how differential vowel prolongation can be used to enhance fluency.