SPEECH MECHANISM

 

 Speech Mechanism.

To communicate orally we use speech organs. Speaking seems very simple activity but it is not. It requires a lot of efforts and practice to tune speech organs to speak correctly. Hence, production of speech is considered as a tough process and complicated process. The whole process which include a series of many events is called speech mechanism. It is very important to understand the speech mechanism to utter words correctly. the speech organs are divided into three systems as shown below- 

Speech mechanism involves many events like

1.     Psychological events:

                           i.          Central nervous system-It includes brain and spinal cord which help to think and prepares organs to speak.

                         ii.          Peripheral nervous system: it includes thousands and lakhs of nerves spread all over the body. It helps to transmit the message, receive the message and coordinate among speech organs.

2.     Physiological events:

                           i.          Articulation: Movements of various speech of organs.

                         ii.          Breathing: The circulation of air from outside to inside (inhale)and from inside to outside (exhale).

3.     Acoustic events:

                           i.          The disturbance in the airflow by the speech of organs comes into acoustic events.

Speech mechanism includes four  main mechanisms

 

1.     Air stream mechanism (process)- It is a source of air for the production of sound.

2.     Phonation mechanism (process)- It involves the behavior of vocal cords in larynx.

3.     Oral-nasal mechanism (process)- it involves closure of either oral or nasal cavity.

4.     Articulation mechanism (process)- it involves movements of speech organs.

A.    AIR-STREAM MECHANISM

A very important part of a speech mechanism is the air flow. With out air no sound can be produced. We inhale and exhale air continuously, without break. This breathing helps us to continue air flow between environment and our lungs through air tract. Sound are produced when organs of speech create disturbances in the air flow in different ways. There are three air stream mechanisms which make speech mechanism possible.

Types of Air-Stream Mechanism

In phonetics, the air-stream mechanism is the method by which airflow is created in the vocal tract. Along with phonation and articulation, it is one of three main components of speech production. There are two types of airstreams or ways that air can flow: inward and outward.

       i.          Inward flow of air – air comes in from outside through our mouths. This flow is called ingressive.

     ii.          Outward flow of air– Air starts from within us somewhere (lungs, etc.) and flows out through our mouth. This outwards flow is called egressive. It is a positive pressure.

The organ generating the air-stream is called the initiator and there are three initiators

the lungs (together with the diaphragm and the ribs), the glottis, and the tongue. On the basis of initiators air streams are of three types-

1.     Pulmonic Air-stream mechanism

2.     Glottalic Air-stream Mechanism

3.     Velaric Air-stream Mechanism

1.     Pulmonic Air-stream mechanism

Breathing as a live maintaining exercise in which lungs plays an important role as they serve as a reservoir (store) of air. Pulmonic Air-stream mechanism includes lungs, diaphragm and respiratory muscles. The walls of the lungs act as an initiator. Respiratory muscles push and pulls the diaphragm so that either air pushed outside or comes inside the lungs. Most sounds are produced with a pulmonic airstream mechanism.it is of two types- Pulmonic egressive and Pulmonic ingressive

2.     Glottalic Air-stream Mechanism

It is the second air-stream mechanism in speech mechanism. It includes larynx, vocal coeds and glottis. The closed glottis acts as an initiator and the air in the larynx is used to create pressure. It has two types of flows- Glottalic egressive and Glottalic ingressive.

3.     Velaric Air-stream Mechanism

Velaric air-stream mechanism used air in the mouth cavity and the initiator is tongue. Movement of mouth air is created by the action of tongue. Clicks of tongue produced velaric airstream mechanism. It is of two types - Velaric egressive and Velaric ingressive

 

B.    PHONATION MECHANISM

Phonation is the mechanism which takes place when voice is produced in the speaking. During phonation air stream moves up and enters the trachea or wind pipe of larynx. It includes larynx, vocal cords and glottis.

1.     Larynx: The phonation process occurs at the larynx. It is the main organ of phonation. It is found at the top of the trachea. Larynx has two horizontal folds of tissue in the passage of air; they are the vocal folds. The gap between these folds is called the glottis.

2.     Vocal cords: Vocal cords are a pair of muscles and cartilages. These are specialized to move at various degree. These may come closure or they may set apart from each other. Their position result in opening and closing of glottis.

3.     Glottis: it is small opening between two vocal cords. When vocal chords are apart glottis is open while vocal cords are nearer the glottis is closed. The opening and closing of glottis gives distinct variety to the sounds. There can be four stages of glottis

                           i.          Open glottis (breathe/ voiceless stage)

                         ii.          Glottis in vibration (voiced stage)

                       iii.          Closed glottis (glottis stops are produced)

                       iv.          Narrowed glottis (whisper stage)

 

C.    ORAL-NASAL MECHANISM

It is an important mechanism which include the movement of velar in the mouth. Velum is the rear end of mouth roof. It is also called the soft palate. During the speech mechanism, it acts as a valve in closing and opening of the nasal cavity. It has two positions-

1.     Upward- when velum is upward and backwards it stops the path of nasal cavity and then the sound produced are called oral sounds because now the air flows through mouth and goes out. Closing of the nasal path is called velic closure.

2.     Downwards- When velum moves downwards and the back of the tongue moves upwards the passage of the oral cavity is closed and air passes through the nasal cavity. The sounds produced in this condition are called nasal sounds. it closes the path of oral cavity. The opening of the nasal path is called velic opening.

 

D.    ARTICULATORY MECHANISM

Finally, the articulation process is the most obvious and important too. It is the third element of speech production. Articulation is the term used for all actions of the organs of the vocal tract that effect modifications of the signal generated by the voice source. It takes place in the mouth and we can differentiate most of the speech sounds with the help of this mechanism. In the mouth, oral cavity acts as a resonator while tongue, lips, mouth roof are called articulators.

Among the articulators we have

1.     Upper lip and lower lip

 

2.     upper and lower teeth,

3.     tongue (tip, blade, front, back) and

4.     roof of the mouth (alveolar ridge, palate and velum)

5.     uvula etc.

On the basis of the place and manner of articulation, sounds are distinguished from each other. Articulation performance is classified by

1.     the place of articulation (usually the location of the maximum constriction of the vocal tract),

2.     the manner of articulation (stricture, tap or trill),

3.     nasality and

4.     degree of laterality.

Articulators are of two types: active and passive.

1.     Active articulators move and touch other organs at different places to produced distinct sounds.

2.     Passive articulators give place to the active articulators so that they can touch them and perform the speech articulation mechanism.