The opening of the vocal folds takes different positions:
v. 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/.
vi. 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.
vii. 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).
viii. 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.