Wave-flow index: A measure of vocal efficiency

A measure called "wave-flow index" is proposed for examining phonatory functions. Advantages of using the wave-flow index are: (1) Measurement is non-invasive and easy. (2) Physical meaning is clear. (3) Measuring device can be simple, small and inexpensive, Basic notion of the index is the ratio of wave component to the flow component both measured outside the mouth. Actually, the wave component corresponds to the vocal intensity and the flow component corresponds to the mean airflow rate. The both components are represented in dB for convenience. The wave-flow index is considered to be closely related to the efficiency of the glottis under certain limited conditions.