Yuling Yan

Automatic tracing of vocal-fold motion from high-speed digital images

Defining characteristics of the phonatory vocal fold vibration is essential for studies that aim to understand the mechanism of voice production and for clinical diagnosis of voice disorders. The application of high-speed digital imaging techniques to these studies makes it possible to capture sequences of images of the vibrating vocal folds at a frequency that can resolve the actual vocal fold vibrations of a patient. The objective of this study is to introduce a new approach for automatic tracing of vocal fold motion from image sequences acquired from high-speed digital imaging of the larynx. The approach involves three process steps. 1) Global thresholding-the threshold value is selected on the basis of the histogram of the image, which is assumed to follow Rayleigh distribution; 2) applying a morphology operator to remove the isolated object regions; 3) using region-growing to delineate the object, or the vocal fold opening region, and to obtain the area of the glottis; the segmented object obtained after global threshold and the morphological operation is used as a seed region for the final region-growing operation. The performance, effectiveness and validation of our approach is demonstrated using representative, high-speed imaging recordings of subjects having normal and pathological voices.

Investigation of voice initiation and voice offset characteristics with high-speed digital imaging

This study involves preliminary investigation of the characteristics of the voice initiation period (VIP) and voice offset period (VOP) using high-speed digital imaging. The goals of the study were to develop a methodology to objectively analyze these periods of phonation and to explore the feasibility of studying the effects of aging on these phonation segments. Results of the analysis of the data from two female subjects, one younger and one older, with the developed methodology, demonstrated that the older subjects VIP was characterized by a slow and irregular increase in glottal area waveform (GAW) until reaching 90% of the maximum opening of the glottis at 244 frames or 122 ms. The younger subject demonstrated a sharp increase in GAW during VIP, taking only 155 frames or 77.5 ms to reach the 90% mark. Also, the older subject took a greater number of frames for the vocal fold vibration to come to a complete stop than the younger subject during the VOP; 275 frames and 150 frames respectively.