Shared structure and divergent phonetic grammars: prosodic fine-tuning of vowel nasalization in Australian and American English

This study examines how prosodic structure regulates coarticulatory vowel nasalization in Australian English (AusE) and how this system compares with American English (AmE). Adopting a phonetic-grammar framework in which prosody serves as a structural scaffold for phonetic implementation, we manipulate focus-driven prominence and prosodic boundary strength to investigate two interrelated dimensions of nasality: nasal consonant duration and time-varying vowel nasalization. For direct comparisons, the experimental design mirrors prior work on AmE (Cho et al., 2017) and explicitly models potential phonation (glottalization) confounds. Results show that AusE and AmE share a prosodic-structural conditioning of nasality. In both dialects, prominence enhances the nasal consonant while inducing coarticulatory resistance in the adjacent vowel; and boundary effects show an asymmetry across phrase edges, with nasal duration and vowel nasalization reduced phrase-initially and enhanced phrase-finally. Crucially, however, shared prosodic organization does not entail phonetic identity. AusE shows stronger focus-induced coarticulatory resistance than AmE. Importantly, this difference is not a uniform shift in magnitude or temporal extent, but a dynamic modulation over the vowel’s time course in both carryover (NVC) and anticipatory (CVN) contexts. This difference persists after including glottalization (stronger under focus in AusE) as a covariate, implying genuine differences in velopharyngeal coordination. Moreover, such modeling reveals a stronger domain-initial boundary effect on vowel nasalization (initial reduction in NVC) in AusE than in AmE. We conclude that dialectal variation operates at the level of phonetic grammar with reference to prosodic structure: while AusE and AmE share abstract phonological categories and prosodic representations, they differ systematically in the fine-tuning of control parameters at the phonetics–prosody interface, differentially balancing system-oriented efficiency and output-oriented distinctiveness.