Acoustic-phonetic variation in word-final alveolar consonants in speech to infants with and without hearing loss.

Abstract

Relatively little work has examined acoustic-phonetic variability in consonants in infant-directed speech, particularly that directed to children with hearing loss. Assimilation is a form of variability which has been particularly well studied in adult-directed speech in which a word-final alveolar consonant takes the place of articulation of a following word-initial consonant (as when /n/ in cotton sounds like /m/ in the phrase cotton[m] balls). Two studies examined types of acoustic-phonetic variation in assimilable environments, defined as contexts in which a word-final alveolar stop (oral or nasal) is adjacent to a word-initial labial or velar consonant, in speech directed to adults and to infants with and without hearing loss. First, waveform, spectral, and perceptual information were used to classify tokens of word-final alveolar stops into four categories: assimilated, canonical, glottalized, or deleted. Next, the second formant, F2, was measured in a subset of these tokens, to gauge the extent of place assimilation in assimilable contexts. Preliminary results show substantial phonetic and acoustic variability in assimilable environments in infant-directed speech, but the extent of this variability appears similar to that in adult-directed speech. These findings have implications for understanding language development in normal-hearing children and children with hearing loss.