The various organs which are involved in the production of speech sounds are called speech organs (also known as vocal organs). The study of speech organs helps to determine the role of each organ in the production of speech sounds. They include the lungs, the vocal folds, and most importantly the articulators.
1. The LungsThe airflow is by far the most vital requirement for producing speech sound, since all speech sounds are made with some movement of air. The lungs provide the energy source for the airflow. The lungs are the spongy respiratory organs situated inside the rib cage. They expand and contract as we breathe in and out air. The amount of air accumulated inside our lungs controls the pressure of the airflow.
2. The Larynx & the Vocal FoldsThe larynx is colloquially known as the voice box. It is a box-like small structure situated in the front of the throat where there is a protuberance. For this reason the larynx is popularly called the Adam’s apple. This casing is formed of cartilages and muscles. It protects as well as houses the trachea (also known as windpipe, oesophagus, esophagus) and the vocal folds (formerly they were called vocal cords). The vocal folds are like a pair of lips placed horizontally from front to back. They are joined in the front but can be separated at the back. The opening between them is called glottis. The glottis is considered to be in open state when the folds are apart, and when the folds are pressed together the glottis is considered to be in close state.
The opening of the vocal folds takes different positions:
- Wide Apart: When the folds are wide apart they do not vibrate. The sounds produced in such position are called breathed or voiceless sounds. For example: /p/f/θ/s/.
- Narrow Glottis: If the air is passed through the glottis when it is narrowed then there is an audible friction. Such sounds are also voiceless since the vocal folds do not vibrate. For example, in English /h/ is a voiceless glottal fricative sound.
- Tightly Closed: The vocal folds can be firmly pressed together so that the air cannot pass between them. Such a position produces a glottal stop / ʔ / (also known as glottal catch, glottal plosive).
- Touched or Nearly Touched: The major role of the vocal folds is that of a vibrator in the production of speech. The folds vibrate when these two are touching each other or nearly touching. The pressure of the air coming from the lungs makes them vibrate. This vibration of the folds produces a musical note called voice. And sounds produced in such manner are called voiced sounds. In English all the vowel sounds and the consonants /v/z/m/n/are voiced.
Thus it is clear that the main function of the vocal folds is to convert the air delivered by the lungs into audible sound. The opening and closing process of the vocal folds manipulates the airflow to control the pitch and the tone of speech sounds. As a result, we have different qualities of sounds.
3. The ArticulatorsArticulators transform the sound into intelligible speech. They can be either active or passive. They include the pharynx, the teeth, the alveolar ridge behind them, the hard palate, the softer velum behind it, the lips, the tongue, and the nose and its cavity. Traditionally the articulators are studied with the help of a sliced human head figure like the following:
b. The Hard Palate: The hard palate is the concave part of the roof of the mouth. It is situated on the middle part of the roof.
c. The Velum or Soft Palate: The lower part of the roof of the mouth is called soft palate. It could be lowered or raised. When it is lowered, the air stream from the lungs has access to the nasal cavity. When it is raised the passage to the nasal cavity is blocked. The sounds which are produced touching this area with the back of the tongue are called velarsounds. For example: /k/g/.
b. Spread: The lips can be spread. In this position the lips are moved away from each other (i.e. when we smile). The vowel that we articulate from this position is an unrounded one. For example, in English /i: /is a long vowel with slightly spread lips.
c. Neutral: Again, the lips can be neutral, a position where the lips are not noticeably rounded or spread. And the articulated vowel from this position is referred to as unrounded vowel. For example, in English /ɑ: / is a long vowel with neutral lips.
a. The tip: It is the extreme end of the tongue.