Comparison of auto-contouring and hand-contouring of ultrasound images of the tongue surface.

Contours traced by trained phoneticians have been considered to be the most accurate way to identify the midsagittal tongue surface from ultrasound video frames. In this study, inter-measurer reliability was evaluated using measures that quantified both how closely human-placed contours approximated each other as well as how consistent measurers were in defining the start and end points of contours. High reliability across three measurers was found for all measures, consistent with treating contours placed by trained phoneticians as the 'gold standard.' However, due to the labour-intensive nature of hand-placing contours, automatic algorithms that detect the tongue surface are increasingly being used to extract tongue-surface data from ultrasound videos. Contours placed by six automatic algorithms (SLURP, EdgeTrak, EPCS, and three different configurations of the algorithm provided in Articulate Assistant Advanced) were compared to human-placed contours, with the same measures used to evaluate the consistency of the trained phoneticians. We found that contours defined by SLURP, EdgeTrak, and two of the AAA configurations closely matched the hand-placed contours along sections of the image where the algorithms and humans agreed that there was a discernible contour. All of the algorithms were much less reliable than humans in determining the anterior (tongue-tip) edge of tongue contours. Overall, the contours produced by SLURP, EdgeTrak, and AAA should be useable in a variety of clinical applications, subject to spot-checking. Additional practical considerations of these algorithms are also discussed.

Effects of Ultrasound Familiarization on Production and Perception of Nonnative Contrasts.

BACKGROUND/AIMS: We investigated the efficacy of ultrasound imaging of the tongue as a tool for familiarizing naïve learners with the production of a class of nonnative speech sounds: palatalized Russian consonants. METHODS: Two learner groups were familiarized, one with ultrasound and one with audio only. Learners performed pre- and postfamiliarization production and discrimination tasks. RESULTS: Ratings of productions of word-final palatalized consonants by learners from both groups improved after familiarization, as did discrimination of the palatalization contrast word-finally. There were no significant differences in the improvement between groups in either task. All learners were able to generalize to novel contexts in production and discrimination. The presence of palatalization interfered with discrimination of word-initial manner, and ultrasound learners were more successful in overcoming that interference. CONCLUSION: Ultrasound familiarization resulted in improvements in production and discrimination comparable to audio only. Ultrasound familiarization additionally helped learners overcome difficulties in manner discrimination introduced by palatalization. When familiarizing learners with a novel, nonnative class of sounds, a small set of stimuli in different contexts may be more beneficial than using a larger set in one context. Although untrained production can disrupt discrimination training, we found that production familiarization was not disruptive to discrimination or production.