The influence of accents in australian English vowels and their relation to articulatory tract parameters

In this paper we analyse and compare a low dimensional linguistic representation of vowels with high dimensional prototypical vowel templates derived from a native Australian English speaker. We further perform the same analysis on Lebanese and Vietnamese accented English to investigate how di erences due to accents impact on such a representation. In a low dimensional linguistic representation a vowel is characterised by articulatory tract parameters. To simplify the problem, the study is restricted to vowels that, notionally at least, involve a steady state articulation i.e. a stable target con guration of tongue, lips and jaw between preceding and following articulatory transitions. Vowels are represented by the horizontal and vertical position of the part of the tongue involved in the key articulation of a particular vowel, e.g., high or low and front or back. To this is added lip posture, spread or rounded. Prototypical vowel templates are derived as follows. The sound pressure signal is parametrized by 12 mel-frequency cepstrum coe cients. At the centre of each phonetically labelled segment, 180 dimensional phone templates are extracted. For the group of short (/I/, /E/, /A/, /O/, /V/, /U/, /@/) and long vowels (/i:/, /e:/, /a:/, /o:/, /u:/, /@:/) we obtain vowel clusters by averaging over all templates of each vowel class and accent. The speech materiaThe speech material is taken from the Australian National Database Of Spoken Language (ANDOSL). For a comparison of high dimensional vowel clusters derived from speech samples with low dimensional prototypical vowels in the articulatory tract representation we perform a reduction in dimension by a multidimensional scaling transformation in a two dimensional space. Here, a linear transformation maps a high dimensional space on a lower dimensional sub space by optimising the relative distances between data vectors. As an important result we nd. i) /@/ and /@:/ are surrounded by the remaining vowels; ii) the overall structure and the relative distances between the prototypical vowels are very similar. Variations in the structure can be explained by the in uence of native Australian English, Lebanese Arabic and South Vietnamese accents.