The [s → ʃ] sound change in /str-/ contexts: Acoustic and perceptual results

Abstract

Since 1995 [Shapiro, M. A case of distant assimilation: /str/ → /ʃ tr/. American Speech, 70, 101–107], many studies have noted a sound change occurring in some dialects of English with /s/ in the context /strV/ surfacing as [ʃ trV]. At first the phenomenon was restricted to certain contexts, though studies disagree on which; increasingly, those who produce the change do so in all contexts. Is the fricative is truly identical to / ʃ / as produced by the same speaker? Or is it acoustically on a continuum, though perhaps perceived as one category or the other? In a corpus of real words, speaker W1 was perceived as exhibiting the sound change, and her /s/ spectra in /str/ context were distinctly different from her /s/ spectra in other contexts. However, speaker M1, though not perceived as exhibiting the sound change, showed spectral differences similar to W1’s. Here, acoustic measures that we have developed to characterize the [s → ʃ] difference will be applied to a more extensive corpus, and will also be related to results of formal perception tasks for multiple listeners. It is anticipated that a continuum will emerge, with perceptual classification into categories resulting in the reported sound change.