Acoustic distinctions between intelligible and unintelligible vowels in the speech of the deaf

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The purpose of this study was to determine if systematic differences in F1,F2, and duration distinguished intelligible and unintelligible vowels in the speech of the deaf. Five deaf speakers produced 35 tokens of selected vowels in CVC monosyllabic words. The intelligibility of the vowel was rated on a 1–5 scale by three listeners familiar with the speech of the deaf. Differences between the deaf speakers and a control group of speakers with normal hearing were noted in mean formant values and token‐to‐token variability in F1 and F2. These differences were present even in the most intelligible samples produced by the deaf subjects. In general, relatively large differences in F1 and F2 were present for intelligible and unintelligible productions in the speech of the deaf talkers. Further, token‐to‐token variability in F1 and F2 was greater for the unintelligible than the intelligible productions. There was, however, some overlap of the distribution of intelligible and unintelligible tokens, suggesting that other acoustic dimensions in addition to formant values contributed to perceived intelligibility. No obvious relationship between duration and intelligibility was noted. [Work supported in part by the Easter Seal Research Foundation.]