Subject-Specific Biomechanical Modelling of the Oropharynx: Towards Speech Production.

Biomechanical models of the oropharynx are beneficial to treatment planning of speech impediments by providing valuable insight into the speech function such as motor control. In this paper, we develop a subject-specific model of the oropharynx and investigate its utility in speech production. Our approach adapts a generic tongue-jaw-hyoid model (Stavness et al. 2011) to fit and track dynamic volumetric MRI data of a normal speaker, subsequently coupled to a source-filter based acoustic synthesizer. We demonstrate our model's ability to track tongue tissue motion, simulate plausible muscle activation patterns, as well as generate acoustic results that have comparable spectral features to the associated recorded audio. Finally, we propose a method to adjust the spatial resolution of our subject-specific tongue model to match the fidelity level of our MRI data and speech synthesizer. Our findings suggest that a higher resolution tongue model - using similar muscle fibre definition - does not show a significant improvement in acoustic performance, for our speech utterance and at this level of fidelity; however we believe that our approach enables further refinements of the muscle fibres suitable for studying longer speech sequences and finer muscle innervation using higher resolution dynamic data.