Cues to Vowels in the Aperiodic Phase of English Plosive Onsets

This thesis addresses the problem of vowel recognition in coarticulatory theory and phonology by assessing how early vowel quality can be recognised from English onset plosives realised with aspiration. Particular attention is paid to aspects of production and perception timing. A gating experiment was used to assess how reliably listeners can recognise English monophthongs.
The treatment of coarticulation distinguishes between phonetic and phonological aspects of production and perception, with a clear demarcation between these levels of representation. The results are interpreted through the lens of prosodic phonology, as this framework constrains the grammar more optimally than segmental-phonemic ones and better exemplifies listeners’ sensitivity to the distribution of FPD.
Velar and bilabial onsets give rise to significantly more correct responses than alveolars, which require more precise articulations. High vowels are recognised more reliably than low ones. This result is due to their intrinsically shorter duration, making high vowels less variable through time. This perceptual link is proportionate to the total amount of variation in vowel inherent spectral change (VISC), which corresponds to spectro-temporal variation in formant centre frequencies through time in vowel realisations. Nasal rimes give rise to a smaller proportion of correct responses than non-nasal rimes, especially in the context of high and low front vowels: the VISC and changes in vowel height undergone in the context of such articulations, as well as the phonetic consequences of the overall articulatory constellation shape the resulting percept. CVCs with non-nasal rimes give rise to more correct responses than CVVs, despite there being more articulations on-going: the shortness of the vowel in CVCs compensates for this deficit, making perception more robust. Word frequency does not have a significant effect on recognition for any of the syllable types investigated.
Overall, a much larger temporal window than the phoneme is required for the robust processing and perceptual integration of speech. Phonemes alone cannot adequately define how the relationship between the phonetic co-extensiveness of different sounds and feature sharing is to be accounted for in speech understanding. Since articulators are in constant motion during production, and consonantal gestures have distinctive coarticulatory influences over vocalic ones, the formant frequencies for both types of sound are in constant flux. This variation reinforces perceptual cohesion and has systematic effects on the mapping of FPD, through which larger structures become audible.