[Development of ultrasound laryngography and its phonetic significance].

A new laryngeal imaging system, namely, ultrasound laryngography, has been developed. Vocal fold vibration in M-mode image can be obtained by adjusting the cursor line to the desired level of the vocal fold in B-mode image. In addition, waveforms obtained by M-mode, variant M-mode, pulse transmission and other method can be recorded simultaneously. (1) Simultaneous recording of M-mode, variant M-mode and pulse transmission method during phonation. Seven male adults of unknown vocal pathology were asked to phonate the vowel /e/ and vocal fold vibration was recorded by ultrasound laryngography. Two types of M-mode image of the free margin were obtained. In one type, M-mode image recorded at the upper part of the vocal fold was found to be bright in the closed and opening phase and was displayed as ascending lines from the closed to opening phase. In the other type, M-mode image recorded at the lower part was bright in the closing and closed phase and was displayed as convex curves. Open quotients were measured by pulse transmission method at the upper, middle and lower part of the vocal fold, respectively. The mean value at the middle part was the smallest among the three parts. In waveforms obtained by variant M-mode method of the upper and lower part of the vocal fold, a negative peak was found in the closing and opening phase, respectively. (2) Observation of vocal attack. Vibration mode of three types of vocal attack was investigated by ultrasound laryngography with simultaneous recording of air flow rate using a constant-temperature, hot wire anemometer. i) Hard attack: by M-mode and pulse transmission method, the glottis remained closed until vocal fold vibration is initiated. Air leakage was not observed before the beginning of vocal fold vibration. ii) Soft attack: the glottis was slightly open and air flow rate was gradually increasing before vocal fold vibration is initiated. iii) Breathy attack: the glottis was widely open and a considerable air leakage was observed prior to the initiation of vocal fold vibration. iv) Among all vocal attacks investigated, changes in the variant M-mode waves were observed before the beginning of phonation, suggesting that minute movements of the surface are initiated before the onset of vocal fold vibration.