Australian English monophthong change across 50 years: static versus dynamic measures

Most analyses of monophthong change have historically relied on static acoustic measures. It is unclear the extent to which dynamic measures can shed greater light on monophthong change than can already be captured using such static approaches. In this study, we conducted a real-time trend analysis of vowels in corpora collected from female Mainstream Australian English (MAusE) speakers under 30 years of age across three time periods: the 1960s, 1990s, and 2010s. Using three different methods for characterising the first and second formants (the target-based approach, discrete cosine transform (DCT), and generalised additive mixed model (GAMM)), we statistically examined differences for each of 10 monophthongs to outline change over the fifty-year period. Results show that all three methods complement each other in capturing the changing vowel system, with the DCT and GAMM analyses superior in their ability to provide greater nuanced detail that would be overlooked without consideration of dynamicity. However, if consideration of the vowel system as a whole is of interest (i.e., the relationships between the vowels), visualising the vowel space can facilitate interpretation, and this may require reference to static measures. We also acknowledge that locating the source of vowel dynamic differences in sound change involves reference to surrounding phonetic context.