The variable opening between the vocal folds, acts as a valve the glottis typically assumes 3 positions in the production of speech: tightly closed with air pent up beneath it as in the production of plosives and the glottal stop open as for normal breathing loosely together, acting as a vibrator; this is their typical position in the production of speech; the vocal folds are brought loosely together so that they vibrate when subjected to the airstream coming from the lungs; this vibration is responsible for voicing.