Spectral contrast reduction in Australian English /l/-final rimes

Abstract

Vowel contrasts may be reduced or neutralized before coda laterals in English [Bernard (1985). The Cultivated Australian: Festschrift in Honour of Arthur Delbridge, pp. 319–332; Labov, Ash, and Boberg (2008). The Atlas of North American English, Phonetics and Sound Change (Gruyter Mouton, Berlin); Palethorpe and Cox (2003). International Seminar on Speech Production (Macquaire University, Sydney, Australia)], but the acoustic characteristics of vowel-lateral interaction in Australian English (AusE) rimes have not been systematically examined. Spectral and temporal properties of 16 pre-lateral and 16 pre-obstruent vowels produced by 29 speakers of AusE were compared. Acoustic vowel similarity in both environments was captured using random forest classification and hierarchical cluster analysis of the first three DCT coefficients of F1, F2, and F3, and duration values. Vowels preceding /l/ codas showed overall increased confusability compared to vowels preceding /d/ codas. In particular, reduced spectral contrast was found for the rime pairs /iːl-ɪl/ (feel-fill), /ʉːl-ʊl/ (fool-full), /əʉl-ɔl/ (dole-doll), and /æɔl-æl/ (howl-Hal). Potential articulatory explanations and implications for sound change are discussed.

Perceptual vowel contrast reduction in Australian English /l/-final rimes

“…machine learning algorithms trained on dynamic formant data and duration data were unable to discriminate between the members of these pairs (Szalay et al, 2021). Acoustic contrast between /ʉː-ʊ/ and /əʉ-ɔ/ is partially neutralized before a coda /l/, due to the lowering of the second formant of /ʉː/ (Palethorpe & Cox, 2003;Cox & Palethorpe, 2004;Szalay et al, 2021). Contrast between /aeɔ-ae/ is partially neutralized before coda laterals, as /l/ and the second element of the diphthong overlap substantially.…”

“…In particular, the members of the pairs /iː-ɪ, ʉː-ʊ, aeɔ-ae/ and /əʉ-ɔ/ might be inherently acoustically ambiguous in the prelateral environment, as Cox and Fletcher (2017). machine learning algorithms trained on dynamic formant data and duration data were unable to discriminate between the members of these pairs (Szalay et al, 2021). Acoustic contrast between /ʉː-ʊ/ and /əʉ-ɔ/ is partially neutralized before a coda /l/, due to the lowering of the second formant of /ʉː/ (Palethorpe & Cox, 2003;Cox & Palethorpe, 2004;Szalay et al, 2021).…”

“…Cox (2006) did not find acoustic contrast reduction between the targets of the vowels /iː-ɪ/; however, acoustic contrast between the formant trajectories of /iː-ɪ/ was reduced due to reduction in the onglide of /iː/, which is one of the differentiating features between the two vowels. In addition, both /iː/ and /ɪ/ gain a schwa-like offglide in the prelateral context, which reduces acoustic contrast between their formant trajectories (Palethorpe & Cox, 2003;Szalay et al, 2021). As a result of the vowel-lateral coarticulation, prelateral allophones of AusE vowels differ substantially from their preobstruent counterparts in both spectral and durational characteristics (Palethorpe & Cox, 2003;Szalay et al, 2021).…”

“…Another segment that has been shown to have a strong coarticulatory influence on the preceding vowel is dark coda /l/ (Recasens, 2002;Cox & Palethorpe, 2007). Unlike nasals, coda /l/ affects cues that are contrastive in the English vowel inventory, as it reduces spectral cues to vowel contrast (Palethorpe & Cox, 2003;Szalay, Benders, Cox, Palethorpe, & Proctor, 2021;Wade, 2017). For instance, in Australian English, acoustic vowel contrast is reduced in the prelateral context, in particular between the vowels /iː-ɪ/ (heel-hill), /ʉː-ʊ/ (fool-full), /aeɔ-ae/ (howl-Hal), and /əʉ-ɔ/ (dole-doll) 1 (Palethorpe & Cox, 2003;Szalay et al, 2021).…”

“…Unlike nasals, coda /l/ affects cues that are contrastive in the English vowel inventory, as it reduces spectral cues to vowel contrast (Palethorpe & Cox, 2003;Szalay, Benders, Cox, Palethorpe, & Proctor, 2021;Wade, 2017). For instance, in Australian English, acoustic vowel contrast is reduced in the prelateral context, in particular between the vowels /iː-ɪ/ (heel-hill), /ʉː-ʊ/ (fool-full), /aeɔ-ae/ (howl-Hal), and /əʉ-ɔ/ (dole-doll) 1 (Palethorpe & Cox, 2003;Szalay et al, 2021). Therefore the quality of the nucleus in these words can be attributed to the coda but may also be interpreted as an intrinsic quality of the vowel.…”