Probe Skewing Effects & Kinect Head-tracking in Tongue Contour Imaging

Probe Skewing Effects & Kinect Head-tracking in Tongue Contour Imaging

Samuel Johnston, Daniel Brenner, Rolando Coto, and Diana Archangeli

The University of Arizona, Tucson, Arizona, USA

The position of the ultrasound probe in relation to the position of the head of the subject (the tilt of the head or probe) may affect the quality and comparability of ultrasound tongue images, compromising the interpretability of the data. The challenge of maintaining alignment of the probe with a subject’s head is a substantial one, often involving immobilization of the head or fixation of the probe beneath the subject’s chin, using helmets, cages, and other mechanical systems of varying complexity (see Stone and Davis (1995) on HATS; Whalen et al. (2005) on OptoTrak and HOCUS; and McLeod and Wrench (2008) on helmets). In the field especially (but also in the laboratory), many subjects, particularly the very young and the very old, may be disinclined to have themselves manipulated in these ways, and sometimes find the physical apparatuses imposing, uncomfortable, too heavy, or even frightening. At the same time, the effects of probe skewing that such contraptions are meant to prevent have yet to be assessed quantitatively.

This study compares control images (no tilt) and images gathered with a tilted head to determine the extent to which control images differ from tilt images. We measure the degree of tilt via Microsoft Kinect, using synchronization software developed in our lab. Kinect provides a low-cost non-invasive alternative to systems like OptoTrak (Whalen et al., 2005) and is a portable system with precise measurement of movements (unlike the image-mixing system used with Palatoglossatron (Baker, 2005)).

Subjects in the experiment produce each of the sounds /æ, ɑ, ɹ, l, t, k, s, ʃ, θ /, selected to induce maximally diverse English language tongue gestures. These extremes of articulation cast a wide net for capturing effects of probe skewing.

Subjects produce and hold each of the target sounds through an arc of head roll, from one side, through 0°roll, to the other side, and back to 0°roll. We will report a fitted distance function of tilted images to 0°images with confidence intervals.

References

Baker, A. 2005. Palatoglossatron 1.0. In University of Arizona Working Papers in Linguistics.

McLeod, S. and Wrench, A. 2008. Protocol for restricting head movement when recording ultrasound images of speech. Asia Pacific Journal of Speech, Language, and Hearing, 11(1):23 – 29.

Stone, M. and Davis, E. P. 1995. A head and transducer support system for making ultrasound images of tongue/jaw movement. Journal of the Acoustical Society of America, 98:3107.

Whalen, D. H., Iskarous, K., Tiede, M., Ostry, D., Lehnert-LeHouillier, H., and Vatikiotis-Bateson, E.2005. The Haskins optically corrected ultrasound system (HOCUS). Journal of Speech, Language,and Hearing Research, 48(3):543.