A photoglottographic (PGG) method with external lighting and sensing

Abstract

Photoglottography (PGG) is a moderately invasive technique to observe glottal movements and vocal-fold vibrations. A light guide is inserted into the pharynx and transglottal light is detected by a photosensor placed on the outer skin below the glottis, or conversely the sensor is placed inside the pharynx and the subglottal cavity is illuminated from outside with a light source. This report evaluates a noninvasive PGG method, in which the hypopharynx is illuminated with a light guide placed on the neck skin at the level between the hyoid bone and thyroid cartilage and a photosensor on the skin near the cricoid cartilage. The light passed through the skin illuminates the lumen of the hypopharynx and the photosensor detects indirect (diffusion) light through the glottis during glottal adduction. Choosing an appropriate location for the light source and photosensor, glottal adduction pattern is observed for voiceless stops and fricatives in low as well as high vowel context. Thus, our diffusion-light PGG potentially overcomes the tongue-position dependency of the detected signals, which has been a major caveat of the conventional PGG methods.