Inter-speaker variability: speaker normalisation and quantitative estimation of articulatory invariants in speech production for French

International audienceSpeech production can be analysed in terms of universal articulatory-acoustic phonemic units shared between speakers. However, speakers’ morphological differences and idiosyncratic articulatory strategies lead to large inter-speaker articulatory variability. Relationships between strategy and morphology have already been pinpointed in the literature. This study aims thus at generalising existing results on a larger database for the entire vocal tract (VT) and at quantifying phoneme-specific inter-speaker articulatory invariants. Midsagittal MRI of 11 French speakers for 62 vowels and consonants were recorded and VT contours manually edited. A procedure of normalisation of VT contours between speakers, based on principal component analysis of mean VT contours, led to an overall reduction of inter-speaker VT contours variance of 84%. On the opposite, the sagittal function (i.e. the transverse sagittal distance along the VT midline), which is the main determinant of the acoustic output, had an overall amplitude variance decrease of only 18%, suggesting that the speakers adapt their strategy to their morphology to achieve proper acoustic goals. Moreover, articulatory invariants were identified on the sagittal variance distribution along the VT as the regions with lower variability. These regions correspond to the classical places of articulation and are associated with higher acoustic sensitivity function levels