The necessary and decisive condition for pronunciation is the vibration of the vocal cords, which converts direct current airflow into alternating current airflow, and converts the kinetic energy of the airflow into acoustic energy.As a source of vibration, the vocal cords can be described by the position, shape, size, and viscoelasticity of the vocal cords. The vibration of the vocal cords is affected by the activity of the vocal muscles of the larynx, the pathological structure of the vocal cords, and the auxiliary organs. The passage between the lips, as a resonant cavity, is affected to a certain extent by the way the vocal cords vibrate, but it is mainly adjusted by its own voicing muscles.
(1) Respiratory system
The power source of voice and speech is the respiratory system, including the lungs, trachea, bronchi, ribs, diaphragm, chest and abdomen.The oral cavity, nasal cavity and pharynx are channels for airflow, while the larynx plays a role in protecting the respiratory tract and regulating airflow in and out of the lungs.The trachea and bronchi are the first passages for gas to enter the lungs.
(2) Sound system
The vocalization phenomenon is manifested as the process of voice production in the throat cavity.Human speech behavior is controlled by the speech center in the left hemisphere of the brain.Starting from the speech center, the autonomic nerve transmits information through the peripheral nervous system to the respiratory muscles, vocal muscles and articulators, thereby regulating the speech organs.The process of speech production is considered to be formed by the coordinated movement of these three systems:
The respiratory system provides sufficient air pressure and airflow to activate and maintain sound.
The vocal cords of the larynx, as a source of vibration, provide sufficient energy and a suitable acoustic spectrum to construct speech sounds.
The phonological organs (tongue, lips, mandible, soft palate and pharyngeal cavity) adjust the shape of the vocal tract to produce different speech sounds, including vowels, diphthongs, plosives, affricates, fricatives, and side sounds With nasal sounds.
These three complex systems coordinate with each other to form human speech sounds.The process of human speech production, like other acoustic phenomena, is composed of a series of pressure waveforms whose characteristics are determined by frequency and sound pressure level.
(3) Articulation system
Human phonological organs can produce many kinds of sounds: some sounds are used for oral communication, so they are called speech sounds.How to accurately construct and produce speech sounds is very important. Therefore, speech intelligibility depends entirely on the speaker’s control over the coordination of related muscles during the process of speech and articulation.