Voicing contrasts and their phonological implications in the speech of articulation-disordered children

Five-year-old articulation-disordered children, some classified as substituters and some as syllable reducers, were compared with normal child and adult controls in their production of voicing contrasts. These contrasts occurred in minimal pairs containing word-final obstruents and in minimal triples containing word-initial stops and /s/-plus-stop clusters in initial position. Measures of vowel duration, voice onset time (VOT), and frequency of use of phonetic voicing were made from spectrograms. In every comparison the substituters' performance resembled that of the normal controls, as did the syllable reducers' use of VOT in stop singles. The syllable reducers used larger vowel duration ratios than the normal controls in a few minimal pairs and used phonetic voicing less often in word-initial /b d g/. The production data and previously reported perception data were examined for evidence that individual syllable reducers had voicing contrasts in underlying phonological form despite their deletions of obstruents in which these contrasts occurred. Most of the syllable reducers appeared to recognize underlying voicing contrasts in at least a few final obstruents and in some of the initial stop singles.