Development of an Intelligent Artificial Larynx

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Based on the preliminary investigation in the first year (1986) on linguistic, physiological and acoustical characteristics of the glottal sound source, three parts of the artificial larynx, namely, detection of biological signal, compilation of control signal and generation of glottal source, were designed and their prototype models were built in the second year (1987). Then, in the third year (1988), those parts were assembled to evaluate the combined characteristics in an experimental set up without surgical operation for the subjects.In the artificial larynx which is proposed in this project as an substitutive voice source for laryngectomized patients, it is aimed to provide capabilities of controlling automatically major paramenters of voiced sound source of speech, such as start and stop of voice source, instant stop of vocal fold vibration at unvoiced consonant, and changes in fundamental frequency and amplitude of voice for prosodic information.As for the start and stop of voice source and the instant stop of vocal fold vibration among those paramenters, possibility of manual control with a specially designed switch device was examined, at the same time, the basic nature of their timing was investigated. This timing switch is to be replaced in the practical stage by residual function of muscules involved in voicing. Possibility of controlling prosodic information conveyed by changes in fundamental frequency and amplitude by using expiratory airflow was also ascertained.As results of those experiments conducted in the third year, defects in the artificial alrynx regarding to quality and clearness of speech sound, easiness of use, and accuracy of operation were remarked, and points to be improved were discussed.