Detecting the edge of the tongue: a tutorial.

The goal of this paper is to provide a tutorial introduction to the topic of edge detection of the tongue from ultrasound scans for researchers in speech science and phonetics. The method introduced here is Active Contours (also called snakes), a method for searching for an edge, assuming that it is a smooth curve in the image data. The advantage of this approach is that it is robust to the noisy speckle that clouds edges. This method has been implemented in several software packages currently used for detecting the edge of the tongue in ultrasound images. The tutorial concludes with an overview of the scale-space and Kalman filter approaches, state-of-the-art developments in image processing that will likely influence work on tongue edge detection in the coming years.