A ultrasonic method makes it possible to observe the movement of the cover and body of the vocal fold simultaneously.
(1) Variant M-mode display
The equipment is almost the same as that used for ultrasonoglottography. Using the gate system of echo selector and callipermarker, effective depth of laryngeal vibration and phase difference of motion of the cover and body of the vocal fold can be measured. The effective depth has a tendency to increase as the loudness increases and to decrease as the pitch increases. The phase difference between two waves has a tendency to increase as the loudness and/or pitch increase.
(2) Ultrasonic real time imaging
Using the real time imaging by ultrasonic pulse method, the movement of marginal and inner layer of the vocal fold during phonation is visualized as a two-dimentional image. We can observe gross movement of the arytenoid, muscular layer and free margin of the vocal fold in horizontal section simultaneously. An average value of the effective depth is about 0.4 mm.
