Vowel identification: orthographic, perceptual, and acoustic aspects

This study investigates conditions under which vowels are well recognized and relates perceptual identification of individual tokens to acoustic characteristics. Results support recent finding that isolated vowels may be readily identified by listeners. Two experiments provided evidence that certain response tasks result in inflated error rates. Subsequent experiments showed improved identification in a fixed speaker context, compared with randomized speakers, for isolated vowels and gated centers. Performance was worse for gated vowels, suggesting that dynamic properties (such as duration and diphthongization) supplement steady-state cues. However, even-speaker-randomized gated vowels were well identified (14% errors). Measures of "steady-state information" (formant frequencies and f0), "dynamic information" (formant slopes and duration), and "speaker information" (normalization) were adopted. Discriminant analyses of acoustic measurements indicated relatively little overlap between vowel categories. Using a new technique for relating acoustic measurements of individual tokens with identification by listeners, it is shown that (a) identification performance is clearly related to acoustic characteristics; (b) improvement in the fixed speaker context is correlated with improved statistical separation resulting from formant normalization, for the gated vowels; and (c) "dynamic information" is related to identification differences between full and gated isolated vowels.