Small knowledge of hearing rehabilitation

Speech sound source is produced in the throat and formed in the vocal tract, which is a resonant cavity composed of pharyngeal cavity, oral cavity, nasal cavity and their accessory organs. When the pulse air flow of sound energy passes through pharyngeal cavity, oral cavity and nasal cavity, it will produce various resonances. The air flow in the oral cavity is regulated by various activities of the voice construction organ, which can produce different sounds.

The vocal tract (oral cavity, nasal cavity and pharyngeal cavity) is connected with the laryngeal cavity, and the nasal cavity is connected with the oral cavity. The oral cavity is the most active organ of voice construction. The tongue moves in the oral cavity in front and back, high and low, changes the shape of the vocal tract of the resonance system, and produces different vowels. Different parts of the tongue and dentition, gingiva, hard palate and soft palate form obstruction and stenosis, forming different consonants. The movement of vocal tract is the source of resonance of speech.

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Oral resonance occurs in the oral area, and a good oral resonance should originate from the surface of the central tongue of the mouth. Tongue position has a great influence on speech sound quality: over front position of tongue tends to lead to anterior focus (i.e. baby tone), behind position of tongue leads to posterior focus, but too low position of tongue will lead to laryngeal focus. There are only three nasal sounds / m, N, ng / in Chinese system that need nasal resonance. Nasal resonance occurs in the nasal cavity. The mouth and nasal cavity are separated by the hard palate (the front of the top of the mouth) and the soft palate (the back of the top of the mouth). Non nasal sounds require the uvula of the soft palate to move upward to close the nasopharynx passage. The nasal sound requires that the uvula of the soft palate should be drooping, and the nasopharynx should be opened rapidly. The sound wave should pass through the uvula of the soft palate and reach the nasal cavity. Some people have too much nasal resonance, while others have too little. Natural speech calls for a harmony between oral and nasal sounds.

Speaking and learning to speak

Air flows out of the lungs, through the lungs, bronchi and trachea, and then to the throat. The vocal cords on both sides are located in the larynx, and the area between the vocal cords is glottis. The opening of glottis is inverted “V”. This position is in the inspiratory process. Air passes through the glottis and reaches the lungs without any resistance. When making a sound, the glottis are closed in the shape of “I”. In the closed state, the exhaled air flows through the glottis, making the vocal cords vibrate. When the vocal cord vibrates, it produces a series of air pulse waves, which are converted into a series of sound energy pulse signals, thus forming the basic sound source of speech, which is the voice (or vocalization). The movement of vocal cords is the vibration source of speech.

Only when the time of glottic closure is consistent with the time of air flow exhalation can natural voice appear. If the glottis are not closed completely, it will make the voice sound too heavy. If the glottis are closed too tightly, the voice will be too harsh. The glottal closure should not be too fast or too slow, which produces a relaxed and harmonious voice.