We have analyzed the dynamic movement of vocal folds during phonation by using the digital fluorography (DF) system. In this paper, the movements of vocal initiation at modal register phonation and at vocal fry phonation were analyzed through the subtracted images offered by DF. As the subtraction technique, time interval difference (TID) mode with two frames was performed on the images obtained at the rate of 30 frames per second.
The results were the followings : in vocal fry phonation, 1) the thickening of the vocal folds downward was observed soon after their adduction finished, 2) the enlargement of the subglottal space due to the increase of subglottal pressure after adduction of vocal folds was smaller than that in modal register phonation, 3) the true and the false vocal folds adducted more strongly than that in modal register phonation, ) the time interval from the beginning of vocal folds adduction to the beginning of phonation was longer than that in modal register phonation.