| As the rapid development of society, the medical technology improved. The advanced medical technology can reduce the physically and psychologically sufferings caused by diseases. In the ENT, the highest morbidity is throat illness. The main diagnosis of throat disease was visual examination in the past. With the development of technology, X-ray examination, histological examination and vocal function tests are used in the inspection of the laryngeal disease. However, these methods give the patients extra pains, and also low accuracy. In the recent decade, with the help of modern medical equipments, voice digital signal processing technology is used in the diagnosis of laryngeal disease, and the medical workers take a deeper and broader study of laryngeal disease and vocal cords vibration mechanism. Researchers improve the vocal cords model gradually after years of analysis of the physical and vibrational structure of the vocal cords organization.From the anatomical structure of the vocal cords and vocal physical mechanism, and taking into account the hierarchical theory of the vocal cords, this paper put forward the dual-spring symmetrical vibration model. The model is based on the physiological characteristics of the vocal cords and muscles elastic motion and aerodynamics. It provides a more reasonable and practical model for vocal folds vibration. This paper selects the proper glottis and sound channel parameters, determines parameters of mass block, spring and damping of the model, and uses the established model to calculate and analyzed the glottis acoustic impedance and dynamic system. Through the electricity-power-sound analogy method, it draws the equivalent circuit diagram of the dynamic system, the equivalent diagram of the glottis and the acoustic impedance and the circuit model diagram of voice signal system of the model. Based on the relevant theory of the physical model, this paper studies quantitative the physical mechanism of vocal fold vibration, and simulates the vibration of vocal cords. The results are analyzed and discussed. We conclude that:lower mass in low frequency produces a larger displacement; lower mass displacement will be reduced when increasing the muscle layer hardness; when the muscle layer, lower mass are very hard, the double spring model will be reduced to a single mass model. Combining with vocal common lesions, and based on the dual-spring symmetrical vibration model, the three mass block symmetric vibration model is proposed. It uses the established model to analyze the glottis acoustic impedance and dynamic system, and it draws the equivalent diagram of the glottis acoustic impedance and the circuit model diagram of voice signal system of the model. According to the equation solution results of this model, it selects a range of parameter values, simulates the three mass block movements, and draws the displacement time image. In the simulation of the three mass symmetric vibration model of the vocal folds, when the vocal cords lesions occur, i.e.,the elasticity coefficient of the lower masses and the coupling elasticity coefficient between the upper two masses are changed, the movement situation will change. The upper part and lower part of the vocal cords will not be able to synchronous vibration. The amplitude of the fore-end and the rear-end of the vocal cords will have obvious differences. The vibration waveform will appear to drift, and so on. Therefore, combining with the theory value and the clinical trial data, the model will be able to be used for laryngeal diseases diagnosis to further study. The theoretical analysis of this article laid the foundation for the model used for throat diseases diagnosis.The research of the model of vocal folds vibration reveals the characteristics of the vocal folds vibration, and it will help people to get a better understanding of the physiological and pathological characteristics of the vocal folds vibration. Compared with previous models, the established model of this paper is more sophisticated, more similar to human tissue and more in line with the physiological characteristics of the human vocal cords. It provides scientific basis in the fields of laryngeal pathology, voice therapy, artificial organs and other medical research. And it has significant and practical values in the fields of the development of new type of acoustic transducer, improving the effect of the existing sound technology and the development of new sound technology. |
