Parametrising Degree of Articulator Movement from Dynamic MRI Data

A new approach is proposed for quantifying the degree of articulator movement within a phoneme as a single scalar value, using vocal tract images captured using dynamic MRI. This indicates the degree of physical movement of the articulators involved in speech production, rather than the acoustic consequences of that movement. We go on to show that this is a valid method for characterising the overall dynamics of the vocal tract, by demonstrating a coefficient of determination (R2) of 0.61 between it and a similarly-defined scalar measure of the acoustic dynamics of the signal. The calculation of the new measure involves production of images showing the exact location of any movement within the vocal tract, and additionally shows this information separately for the initial and final segments of each phoneme. Finally, we demonstrate that although some sounds may involve more movement of the articulators than would be expected from the dynamics of the acoustic signal, it is rare for the degree of articulation derived from the MRI data to be significantly less than expected.