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.
The present study investigates the extent to which code-switching experience modulates short-term cross-linguistic phonetic interference. Three experiments were conducted, each examining a different acoustic parameter in the context of code-switching, a dual language paradigm previously shown to enhance cross-linguistic phonetic interference. Bilinguals’ prior experience with code-switching was assessed using the Bilingual Code-Switching Profile. In Experiment 1, Korean–English bilinguals’ productions of F1 and F2 for the code-switched English vowel /æ/ were compared to monolingual (i.e., non-switched) Korean /e/ and English /æ/. While code-switched English vowels shifted in the direction of monolingual Korean vowels, the results suggest that bilinguals with more code-switching experience exhibited reduced cross-linguistic interference relative to those with less experience. In Experiments 2 and 3, Spanish–English bilinguals’ productions of fricative voicing (Experiment 2) and spirantization of intervocalic voiced stops (Experiment 3) in Spanish and English code-switched tokens were compared to monolingual tokens. Results suggest that participants with greater code-switching experience produced less evidence of cross-linguistic phonetic interference for both fricative voicing and intervocalic spirantization. Collectively, and suggesting a role for executive control mechanisms at the phonetic level, these findings illustrate that code-switching experience serves to mitigate short-term cross-linguistic interference.
Unfamiliar accents can cause word recognition challenges, particularly in noisy environments, but few studies have incorporated quantitative pronunciation distance metrics to explain intelligibility differences across accents. To address this gap, intelligibility was measured for 18 talkers -- two from each of three first-language, one bilingual, and five second-language accents -- in quiet and two noise conditions. The relations between two edit distance metrics, which quantify phonetic differences from a reference accent, and intelligibility scores were assessed. Intelligibility was quantified through both fuzzy string matching and percent words correct. Both edit distance metrics were significantly related to intelligibility scores; a heuristic edit distance metric was the best predictor of intelligibility for both scoring methods. Further, there were stronger effects of edit distance as the listening condition increased in difficulty. Talker accent also contributed substantially to intelligibility models, but relations between accent and edit distance did not consistently pattern for the two talkers representing each accent. Frequency of production differences in vowels and consonants was negatively correlated with intelligibility, particularly for consonants. Together, these results suggest that significant amounts of variability in intelligibility across accents can be predicted by phonetic differences from the listener’s home accent. However, talker- and accent-specific pronunciation features, including suprasegmental characteristics, must be quantified to fully explain intelligibility across talkers and listening conditions.