Effects of vocalic formant transitions and vowel quality on the English [s]-[ŝ] boundary

The effects of the vocalic portion of fricative-vowel syllables on the perception of alveolar and palatal fricatives were examined. The fricative noises were synthesized to represent a continuum from [s] to [ŝ]; the vowels ranged from [u] to [i] through [1] and [ü]. The vocalic formant transitions were of two types, those appropriate to [s] and those to [ŝ]. All stimuli were presented in forced-choice labeling tests. The boundary between [s] and [ŝ] for English-speaking listeners was found to vary as a function both of transitions and of vowel. The effect of the transitions was clear and straightforward: An ambiguous fricative noise was heard more often as [s] before [s] transitions, and as [ŝ] before [ŝ] transitions. The quality of the vowel clearly had an effect, but the interpretation of the effect in terms of the perception of coarticulation was not clear. The responses of listeners who were unfamiliar with languages which use [ü] and/or [1] distinctively were not significantly different from those of listeners who were familiar with such languages.