Towards a dynamical model of English vowels. Evidence from diphthongisation

TL;DR

This study addresses the problem of how to model inherent vowel dynamics in English, particularly gradient diphthongisation and its relation to long monophthongs. It combines an articulatory-acoustic dataset from six Northern English speakers with Articulatory Phonology/Task Dynamics (AP/TD) modelling to test whether diphthongs are best represented as two gestural targets and whether long vowels constitute a separate category. The results show canonical diphthongs strongly align with a two-target gesture representation, while many vowels exhibit gradient diphthongisation that falls between one- and two-target patterns; nonetheless, a two-target framework can account for both extremes and intermediate cases. The modelling demonstrates that long vowels can be equivalently represented as two identical targets or as a single long target, but a two-target depiction is theoretically preferable for linking phonology to phonetics and history, leading to a unified account of diphthongisation and vowel length changes in English.

Abstract

Diphthong vowels exhibit a degree of inherent dynamic change, the extent of which can vary synchronically and diachronically, such that diphthong vowels can become monophthongs and vice versa. Modelling this type of change requires defining diphthongs in opposition to monophthongs. However, formulating an explicit definition has proven elusive in acoustics and articulation, as diphthongisation is often gradient in these domains. In this study, we consider whether diphthong vowels form a coherent phonetic category from the articulatory point of view. We present articulometry and acoustic data from six speakers of Northern Anglo-English producing a full set of phonologically long vowels. We analyse several measures of diphthongisation, all of which suggest that diphthongs are not categorically distinct from long monophthongs. We account for this observation with an Articulatory Phonology/Task Dynamic model in which diphthongs and long monophthongs have a common gestural representation, comprising two articulatory targets in each case, but they differ according to gestural constriction and location of the component gestures. We argue that a two-target representation for all long vowels is independently supported by phonological weight, as well as by the nature of historical diphthongisation and present-day dynamic vowel variation in British English.

Figures (20)

• Figure 1: Mean by-speaker trajectory of TD sensor displacement for each vowel. The beginning and the end of each arrow correspond to the acoustic onset and offset of the vowel respectively.
• Figure 2: Mean by-speaker trajectory of UL sensor displacement for each vowel, relative to normalised time
• Figure 3: The articulatory Euclidean distance depending on the vowel
• Figure 4: TD-UL velocity for two example tokens pronounced by speaker f04. The dashed line represents the acoustic offset of the vowel.
• Figure 5: TD-UL velocity profiles for all the individual vowel tokens