THE AIR-STREAM MECHANISM
To produce speech sound we need an air-stream. Through the experiment we can understand that how it works. When we say ''Ah'' for a long time in whisper, and put our palm in front of mouth, we feel warm air in our palm, which come out from the mouth. When we say ''Baa'' again in whisper and say Ah and baa alternatively for several time, we can see while producing Baa, we close our lips and it prevents air temporarily and when we open lips the air continues to flows out. It modified into speech sound by the movement of organs of our body. It is called Air-stream Mechanism, it can be also called by A Moving of current air. Lung-air is used for most of the speech sound. So, let's look at the respiratory mechanism.
RESPIRATORY MECHANISM:-
Respiratory system consists of the lungs, the muscles of the chest and the windpipe (called trachea).
The lungs are spongy bodies. They are made up of small secs called Alveoli. In this secs the blood is cleaned of its carbon dioxide and provide fresh oxygen from the outer air. The air is supplied to the Alveoli by small tubes called the bronchioles. It come together into two large tubes called the Bronchi, one situated on the right and the other on the left. It join the trachea(windpipe). Through the windpipe the air that we breath in passed through the throat into the lungs. Respiration involves two processes - taking outer air into the lungs called inspiration and throwing out air from the lungs into outer atmosphere called expiration. Expiration is the basis for the articulation of most of the speech sounds. For this reason the air stream involving lung-air which is calles as Pulmonic air- stream.
An air stream is produced by an air-stream mechanism. it is works in exactly the same way as a flit-gun. When we speak, something like the plunger in a flit-gun is in operation, working in the same way as the plunger does in a flit-gun. This is called the initiator. The air stream is set in motion by the initiator, just as the liquid in a flit-gun is set in a motion by the plunger.
There are three main air-stream mechanism...
1. Pulmonic air-stream mechanism
2. Glottic air-stream mechanism
3. Velaric air-stream mechanism
So... let's look at in deep of these three air-stream mechanism...
1. Pulmonic air-stream mechanism:-
In all the languages a very large percentage of speech sounds use a pulmonic air-stream mechanism. It consists of the lungs and the respiratory muscles. The walls of the lungs act as the initiator. They are moved by respiratory muscles so that air is drawn into the lungs or pushed out of them. When the air stream mechanism is used to push air out, it is called Egressive and it is used to draw air in, it is called Ingressive.
Most of the speech sounds make use of s pulmonic egressive air-stream mechanism. It is possible to speak using pulmonic ingressive air-stream mechanism, but no language uses this air-stream to produce speech sounds. We use this air-stream for yawning and snoring, but not for speaking.
2. Glottalic air-stream mechanism:-
The closed glottis acts as the initiator for this and the pharynx is used. For this reason some linguists refer to this air-stream as pharyngeal. Both egressive and ingressive glottalic air-stream mechanisms ar used by some languages of the world for articulation of speech sound. Among Indian languages Sindhi has sounds articulated with a glottalic ingressive air-stream mechanism. These sounds are called Implosives.
3. Velaric air-stream mechanism:-
During this air-stream mechanism, the back of the tongue is the initiator and the air in the mouth is set in motion. That's why, this is also called as the Oral air-stream mechanism. sOund produced with a velaric ingressive mechanism exit in several African languages; sound produced with velaric egressive air-stream mechanism do not exist in any language.
Let's wind up...
So, the air-stream mechanism is very important to produce speech sounds. With help of certain organs of the body it produced the speech sounds. Inhale and Exhale also very important to modify sound.
