Production and perception of lateral-final rimes in Australian English
thesisposted on 28.03.2022, 18:08 by Tünde Orsolya Szalay
English /l/ is a multi-gestural segment produced with dorsal retraction and lowering and a central alveolar closure. In coda position, the tongue dorsum gesture precedes the tongue tip gesture, placing it temporally closer to the vowel gesture. In many varieties of English, including Australian English (AusE), the tongue dorsum gesture has been shown to influence the preceding vowel whereas the tongue tip gesture has been show to be lenited. This thesis examines the production and perception of lateral-final rimes in AusE, first focusing on the effect of coda /l/ on the preceding vowel, and then focusing on coda /l/ lenition. We begin with providing a systematic acoustic analysis of the AusE vowel space in prelateral position compared to pre-obstruent position. Confirming previous research, we find a reduced Fl-F2 vowel plane and spectral contrast reduction between the members of the pairs /ʉ:-ʊ, əʉ-ɔ, æɔ-ae/, and to a lesser extent /iː-ɪ/. We then examine how vowel-lateral coarticulation affects the perception of lateral final rimes, finding that coda /l/ increases the difficulty of vowel disambiguation compared to coda /d/; in particular, reduced perceptual contrast is found between the members of the pairs /ʉ:-ʊ, əʉ-ɔ, æɔ-ae/. We examine listener-speakers' production and perception of duration contrast in /ʉ:-ʊ, əʉ-ɔ, æɔ-ae, iː-ɪ/. We find that listener-speakers producing a longer durational contrast take longer to recognise /l/-final words and are only more accurate when the stimuli contains a larger durational contrast. We attribute spectral and perceptual contrast reduction in prelateral vowels to the coarticulatory influence of the tongue dorsum gesture of /l/. Having examined prelateral vowels, we turn our attention to the articulation and perception of coda /l/ to link our perceptual and articulatory understanding of /l/-vocalisation. Firstly, we contribute to the articulatory characterisation of AusE /l/ by showing that the tongue is elongated in /l/ compared to /d/ due to the simultaneous raising of the tongue tip and the lowering of the tongue dorsum. Secondly, we examine the effect of phonetic context on tongue tip lenition. We find that while speakers produce coda /l/ with a varying magnitude of lenition, they lenite less before a following alveolar and more before a following dorsal consonant due to their articulatory similarity to the coronal and the dorsal gesture of /l/. We link listeners' perception of /l/-vocalisation to articulatory characteristics and phonetic context of coda /l/ and find that while listeners' perception of /l/-vocalisation does not directly correlate with tongue tip lenition, they perceive coda /l/ as more vocalised in contexts in which /l/ is often lenited. This thesis thus provides an in-depth analysis of AusE rimes containing coda laterals, their production, their perception, and implications for a potential sound change. More generally, we also contribute to the understanding of the complex speech sound /l/ by providing further information on the influence of the dorsal gesture on the preceding vowel and lenition of the tongue tip gesture -- abstract.