Recognition of vowels from information in fricatives: perceptual evidence of fricative-vowel coarticulation.

Four studies investigated the perceptual effects of spectral variations in fricatives produced in different vowel contexts. The alveolar and palatal fricatives, [s, z, integral of, 3], were produced by two talkers in the context of the vowels [a, i, u], generating 12 fricative-vowel combinations. A computer-controlled editing procedure was used to excise fricative segments of 150-ms duration, as measured back from vowel onset. These excised segments were used as test stimuli in the four experiments. In the first experiment, fricative identification was highly accurate, especially for segments produced in the [a] context. The results of the subsequent three vowel identification experiments, revealed that the high vowels [i] and [u] were identified 60%--80% of the time in all fricative contexts, with the exception of [i] produced in the context of [integral of]. In contrast, identification scores for [a] were close to chance in all fricative contexts. Acoustic analyses of the stimuli revealed that the fricative segments with high vowel identification scores exhibited clear evidence of spectral changes associated with the vowels, while those segments with the highest fricative identification scores exhibited spectra most similar to fricatives produced in isolation. These results, in combination with more extensive acoustic analyses [S. D. Soli, J. Acoust. Soc. Am. 70, 976--984 (1981)] are discussed in terms of variations in the articulatory compatibility of tongue movements required to produce fricative-vowel sequences.