For the production of speech sounds, there must be some disturbance in the air. Such disturbance is provided by the movement of certain organs of the body such as the muscles of the chest, the vocal cords, the tongue, the lips, and so on. This disturbance, in the form of sound waves, travels to the ear of the listener, who interprets the waves as sounds. The organs of the human body which produce speech sounds are called organs of speech.
1. The Respiratory System
The Respiratory System comprises the lungs, the muscles of the chest, and the windpipe (also called the trachea). The lungs, as we know, perform the function of breathing, or respiration, under the action of the muscles of the chest.
The respiratory system provides an airstream that acts as a source of energy. Without an airstream no amount of activity on the part of the speech organs can produce a sound. This airstream mechanism is called Pulmonic Eggressive Airstream Mechanism.

2. The Phonatory System
The airstream released by the lungs undergoes several modifications before it goes out into the atmosphere. The first such modification is effected in the trachea. If you try to produce the sounds at the beginning of the English words seal and zeal, that is, the s-sound and the z-sound, one after the other, you will notice that there is a certain “hum” in the z-sound, which is not heard in the s-sound. This “hum” is the result of some modifications in the trachea.

i. The Larynx
In the upper part of the trachea is a structure called the larynx, formed of cartilage and muscle, its primary function is to act as valve: when necessary, it closes off the air from and to the lungs and also prevents food etc. from entering the trachea. Its front part is prominent in the throat, and is commonly known as the “Adam’s Apple”. Situated inside the larynx is a pair of lip like structure called Epiglottis in which there lie Vocal cords.
ii. Vocal Cords
These are placed horizontally from front to back, joined at the front but separated at the back. As they are separated at one end, they can assume a large number of positions, but three of them are important:
a. Vocal Cords drawn wide apart:
When the vocal cords are drawn wide apart, there is a wide opening between them called the glottis. Through this opening, the air can pass freely without setting the vocal cords into vibrations. This is the normal position of the vocal cords during the process of breathing. The speech sounds do not have the “hum” when these vocal cords are in this position. They are called voiceless sounds.

b. Vocal Cords held loosely together:
When the vocal cords are held loosely together, the air from the lungs can escape only by setting them into vibration. Such vibration imparts a “hum” to the sounds produced, which are then called voiced sounds. All English Vowels and 15 Consonants are voiced whereas 9 Consonants are voiceless.
Voiced consonants= /b/, /m/, /w/, /v/, /ð/, /d/, /z/, /n/, /1/, /ʒ/, /dʒ/, /r/, /j/, /g/, /ŋ /.
Voiceless consonants= /p/, /f/, /θ/, /t/, /s/, /∫/, /t∫/, /k/, /h/.

c. Vocal Cords held tightly together:
When the vocal cords are held tightly together along their whole length, the glottis is closed, and therefore no air can escape through it. This is the position the vocal cords must take at the time of eating or drinking so that no food or liquid may enter the windpipe.

3. The Articulatory System
After passing through the larynx, the airstream is further modified by the various shapes assumed by the organs of speech lying above the larynx. Before it passes out into the atmosphere, and every such modification affects the quality of the sound produced. These organs of speech, together constituting the articulatory system, are now described.
i. The Pharynx
Extending from the top of the larynx to the hindermost part of the tongue is the pharynx.

ii. The Lips
The lips play an important part in the production of certain speech sounds. The initial sounds in the English words pot and boat, for example, are made by first closing the lips together, and then releasing the closure abruptly. The lip position is an important factor in the production of vowels. Lips can assume a number of positions as stated below.
A. Spread (un-rounded) e.g. Keen
B. Rounded close e.g. Soon
C. Rounded Open e.g. God


iii. The Teeth
Certain consonants are produced with the help of the teeth. Such are the initial sounds in the English words think, that; fan and van.

iv. Roof of the Mouth
Beyond the teeth, in the upper jaw, the whole area is called the Roof of the Mouth, comprising the teeth ridge, the hard palate, the soft palate, and the uvula.
a. The Teeth Ridge
The teeth ridge (also called the alveolar ridge) is the convex part of the roof of the mouth lying immediately behind the upper teeth. It can be easily felt by placing the tongue behind the upper teeth. Many consonant sounds are produced at the teeth ridge. By marking a complete closure at the teeth ridge, followed by a sudden release of the closure, one can produce the /t/ and /d/ sounds in English words ten and day.
b. The Hard Palate
Lying immediately behind the teeth ridge is a hard, bony surface, called the hard palate. It is a curved surface leading to the highest point of the roof of the mouth. At the beginning of the curve are small corrugations that facilitate the movement of food. They also provide obstacles to the outgoing air, thus causing a hissing noise that characterizes the [s] and [f] sounds as in so and show. An example of the sounds produced at the hard palate is the initial sound in the English word yes.
c. The Soft palate
If you move your tongue backwards along the roof of the mouth, you will feel the roof becoming suddenly soft. This soft portion of the roof is called the soft palate or the velum. It is responsible for the production of a large number of sounds such as the initial sounds in the English words king and go. The soft palate can either be raised to make a velic closure or lowered to remove such closure. When raised, no air can escape through the nose; it can escape only through the mouth, and therefore the sounds produced in this state of the soft palate are called oral sounds. Examples of oral sounds are all the sounds contained in the English words take, play, radio and lecture. When lowered, the air can escape through the nose. Here two further possibilities arise: One, if there is a closure at some point in the oral passage, the air can escape through the nose only. The sounds produced are called nasal sounds. Examples are the final sounds in the English words him, hen and hang. Two, if there is no closure at any point in the oral passage the air can escape through the mouth as well as the nose. The sounds are called nasalized sounds.
d. The Uvula
At the very end of the soft palate is a small fleshy pendent structure known as the uvula.

v. The Tongue
The tongue is the most important and the most flexible organ of speech: it can assume a large number of shapes and take many different positions. Most of which are significant from the point of view of speech production. To describe these shapes and positions, it is customary to divide the tongue into different imaginary parts. When the tongue is in the state of rest, the part of it lying behind the lower teeth is called the tip, and that lying against the teeth ridge, the blade, the part against the hard palate is called the front and that against the soft palate, the back. The edges of the tongue are called the rims.
The human vocal system can produce a very large number of different speech sounds. Members of a particulars speech community speaking that particular language, however, use only a limited number of these sounds. Every language makes its own selection of sounds and organizes them into characteristic patterns. This selection of sounds and their arrangement into patterns constitute the phonology of the language.

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