Neighborhood-conditioned phonetic enhancement of an allophonic vowel split.

Abstract

Vowels are enhanced via vowel-space expansion in perceptually difficult contexts, including in words subject to greater lexical competition. Yet, vowel hyperarticulation often covaries with other acoustic adjustments, such as increased nasal coarticulation, suggesting that the goals of phonetic enhancement are not strictly to produce canonical phoneme realizations. This study explores phonetic enhancement by examining how speakers realize an allophonic vowel split in lexically challenging conditions. Specifically, in US English, /æ/ is raising before nasal codas, such that pre-nasal and pre-oral /æ/ are moving apart. Speakers produced monosyllabic words varying in phonological neighborhood density (ND), a measure of lexical difficulty, with CæN or CæC structure to a real listener interlocutor in an interactive task. Acoustic analyses reveal that speakers enhance pre-oral /æ/ by lowering it in Hi ND words; meanwhile, pre-nasal /æ/ Hi ND words are produced with greater degrees of nasalization and increased diphthongization. These patterns indicate that ND-conditioned phonetic enhancement is realized in targeted ways for distinct allophones of /æ/. Results support views of hyperarticulation in which the goal is to make words, that is, segments in their contexts, as distinct as possible.