Phases of the vocal fold vibration cycle

This diagram shows 5 complete cycles of vocal fold vibration, as monitored by a laryngograph. The horizontal axis shows time in ms and the vertical axis shows increasing vocal fold contact. The voice is that of an adult male phonating at approximately 120Hz, using modal ("normal") voice. Note the rapid closing movement and the comparatively slow opening movement.

A & A' = start of closure of vocal folds B = maximum closure of vocal folds

A - B Closing phase B-C Opening phase C-A' Open phase A-C Closed phase

Closed quotient = (A-C)/(A-A') Open quotient = (C-A')/(A-A')