Methods for quantifying tongue shape and complexity using ultrasound imaging

Quantification of tongue shape is potentially useful for indexing articulatory strategies arising from intervention, therapy and development. Tongue shape complexity is a parameter that can be used to reflect regional functional independence of the tongue musculature. This paper considers three different shape quantification methods - based on Procrustes analysis, curvature inflections and Fourier coefficients - and uses a linear discriminant analysis to test how well each method is able to classify tongue shapes from different phonemes. Test data are taken from six native speakers of American English producing 15 phoneme types. Results classify tongue shapes accurately when combined across quantification methods. These methods hold promise for extending the use of ultrasound in clinical assessments of speech deficits.