As we know an air stream is the basis of speech sounds because for the production of speech sounds, we need an air stream. This air stream is produced by an air stream mechanism. There are three main air stream mechanisms: (1) Pulmonic (2) Glottalic and (3) Velaric air stream mechanism. The pulmonic air-stream mechanism: The pulmonic air-stream mechanism consists of the lung and respiratory muscles. The walls of lungs act as initiator.
They are moved so the air is drawn into and pushed out. When this system pushes air out, it is known as ‘egressive’. When this system is used to draw air in, it is ‘ingressive’. Most of the languages use a pulmonic egressive air stream mechanism. A pulmonic ingressive air stream is used but no language sounds are produced. We use this air stream mechanism for yawning and snoring.
Glottalic air-stream mechanism: The second air-stream mechanism is Glottalic air-stream mechanism. The closed glottis acts as the initiator for this and the air in the pharynx is used. For this reason, some linguists refer to this air-stream mechanism as pharyngeal. Both egressive and
ingressive Glottalic air-stream mechanisms are used by some language of the world for the articulation of speech sounds. Among Indian language, Sindhi has sounds articulated with a glottalic ingressive air-stream mechanism.
Velaric air-stream mechanism: The third air-stream mechanism is Velaric air-stream mechanism. The back of tongue is the initiator. Air in the mouth is yet in the motion during this air-stream mechanism. . So it is also known as ‘oral’ air-stream mechanism. Sounds produced with a Velaric ingressive mechanism exist in several African language; sounds produced with a Velaric egressive air-stream mechanism do not seem to exist in any language.
The organs of speech Mechanism:-
For the production of speech sounds, we need an air-stream mechanism and that most sounds of most language in the world are produced with a pulmonic egressive air-stream mechanism. The air that we breathe out comes out of the langs. Before it gets out into the outer atmosphere, various organs in our body convert it into speech sounds. These organs are called the organ of speech mechanism. The organs of speech can be divided into the following three group.
1.The respiratory system. 2. The Phonetary system. 3. The articulatory system.
The respiratory system:-
The respiratory system consists of the lungs, the muscles of the chest and the windpipe (trachea). The lungs are spongy bodies. They are made up small sacs called alveoli. Air is supplied to alveoli by small tubes called the bronchioles. It is through the trachea or windpipe that the air we breathe in passes through the throat into the lungs. The act that is known as respiratory involves two processes. Inspiration-Taking outer air into lungs.
Expiration-Throwing out air from the lungs into the outer atmosphere. The lungs serve as a source of air and the source of energy for
production of speech is generally the air stream coming out of lungs.
(2) The Phonetary system:-
The Phonetary system consists of larynx. The larynx is the little box that is called the ‘Adam’s apple’, situated at the top of the windpipe. The air from the lungs comes out through the windpipe and the larynx. In the larynx, there are situated a pair of like structure called vocal cords and these are placed horizontally from front to back. They are attached in front and can be separated to the back. The opening between the cords is called the glottis is called the glottis. The vocal cards can be opened and closed. The vibration of vocal cords is very significant in speech. When they are kept loosely together, they vibrate and that the vibration produces a musical not called voice. The rate of vibration is called frequency of vibration. This decides the pitch of the voice which helps to create the intonation of a language.
(3) The articulator system:-
The articulatory system consists of the roof the mouth, the tongue, the teeth, the lips.
The roof of the mouth comprises the teeth-ride, the hard palate, the soft palate, and the uvula. The convex bony part of the roof of the mouth which lies immediately behind the upper front teeth is called teeth-ridge. Immediately after the teeth-ridge the roof of the mouth become concave and it is hard and called hard palate. Immediately after the hard palate the roof of the mouth become soft and it called soft palate. The fleshy structure hanging loose at the extreme end of the roof of the mouth is called uvula.
The tongue is most fleecy and is capable of amusing a great variety of position during the articulations of the vowels and consonants. For convenience of description, we divide tongue into four parts: the tip of tongue, the blade of the tongue, the front of the tongue, the back of the tongue. The extreme edge of the tongue is called the tip of tongue. Immediately after the tip is the blade of the tongue. Beyond the blade is
called the front of the tongue. Beyond the front is the back of the tongue.
The teeth acts as passive articulation for producing speech sound. The Lips play their part in the articulation of certain consonant. e.g. /p/, /b/, /m/ are produced with the lips tightly shut. Also the lips play an important part during the articulation of vowel sounds. The lower lip act as an active articulator while the upper lip is a passive.