What Makes a Voice Acoustically Strong
A voice is acoustically strong if the glottal flow can be reduced from a high value to a low value in a short time interval. The total collapse of flow per second is called the maximum flow declination rate. It can be increased by increasing lung pressure, by increasing vibration at the bottom of the vocal fold, or by narrowing the acoustic tube immediately above the vocal folds. In practice, a combination of these control strategies is probably utilized by singers.