Male Vocal Fold Function, low to high
Vocal fold function is the source of the voice sound. It can occur only if the vocal folds are brought together so they may act as a kind of valve that resists the air pressure brought to them by the singer until that air pressure and the vocal fold closure tension meets a balance at which time the vocal fold opens, allowing air to pass and immediately closes again only to have the same process continue at a rate the is represented by the pitch being sung. When singing the A4 immediately above middle C the vocal folds open and close 440 times a second. The A an octave higher will require the folds to open and close 880 times a second. ...