Study on Refined Mechanism Model of Phonation : A Model Taking Vibration of the Vocal Folds and the Resonance in the Vocal Tract into Account

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In voice production of human being, source is produced by self-excited oscillation occurred due to interaction of motion of the vocal folds and a flow through the glottis which is a slot between the left and right vocal fold. In our previous analyses we have collected fundamental data of separated and vibratory air flow which relates the self-excited oscillation directly and performed numerical analysis of normal phonation.Mechanical analyses taking vocal-fold vibration into account is expected to contribute the study on phonation from the mechanical point of view, especially, diagnosis of complicated voice disorders due to property imbalance of the left and right vocal fold caused by diseases such as polyps, and development of artificial-larynxes and esophageal-speech-techniques in which source sound is produced when cancerous vocal folds have been excised.In order to investigate the mechanism of complicated behaviors in the voice disorders due to property imbalance of the left and right vocal fold caused by the diseases, we extended our experimental and theoretical model phonation.We performed the following studies during the term of the project (FY1998-FY1999) :1. We designed a quasi-two-dimensional channel model with an asymmetrical vibratory constriction. We purchased a Laser displacement meter to measure the motion of the constriction and high-accuracy pressure transducers and amplifiers for accurate measurement, and collected fundamental but refined data on steady and unsteady static pressures, flow rate, and so forth.2. Based on the experimental data, we proposed a theoretical model of the vocal folds vibrating asymmetrically. Using this theoretical model, we numerically calculated vibratory pressure and velocity distribution, and so forth.3. We measured normal and abnormal voices, compared the experimental data with the numerical results, and evaluated the measuring methods and the proposed theoretical model.