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.