Voice Production is an aerodynamic phenomenon that transform the air flow to sound signal. Therefore aerodynamic investigation is valuable information about the effciency of the larynx in translating air pressure to acoustic signal. The traditiomal method of measuring subglottic pressure was very invasive and not adequate. So for clinical purpose, a test, that is combination of air pressure measurement during phonation with mean air flow, intensity and frequency, using the airway interruption method is developed. The airway interruption method is noninvasive and easy to perform in clinical cases. Thus this method is very useful for evaluating aerodynamic conditions at the glottis, as well as expiratory force, during phonation. But there are no normal data for Korean, so we studied to obtain normal data.