Study on Speech Production with Normal or Diseased Vocal Folds from the Mechanical Viewpoint.

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In human voice production, air flow from the lung and vibration of vocal folds are coupled at glottis to generate self-excited oscillation which produces sound sources. The sound sources are amplified at upper airway to produce "voice" from the mouth and nostril. The voice production is, therefore, controlled by mechanical mechanism. Hence, normal voice and diseased ones generated by the vocal folds with polyp, cancer, or nerve paralysis were studied jointly by researchers at Nagoya University (NU) and Fujita Health University (FU), aiming at establishing a diagnostic method of the diseases.Research at Nagoya University (NU) :Their previous model of voice production based on normal symmetric vocal folds was improved so that effects of distribution of stiffness, mass, and tension of the vocal folds were included in the model. The improved model was compared with normal voices measured at FU. Furthermore, their previous analytical model on un-symmetric diseased vocal folds was modified to make it easier to compare with data of patients measured at FU.Research at Fujita Health University (FU) :To examine vibration mechanics of normal and diseased vocal folds, sub-and super-glottal pressures and flow rate were measured while motion pictures of the vocal folds were taken using a laryngeal stroboscope. Especially, focusing on small vibration patterns of the sub-and super-glottal pressures, mechanical features of normal and nerve paralyzed vocal folds were studied.Based on the present joint research, further study will be planned.