whistling

Whistling is the production of sound by means of carefully controlling a stream of air flowing through a small hole. Whistling can be achieved by creating a small opening with one's lips and then blowing or sucking air through the hole. The air is moderated by the lips, tongue, teeth or fingers (placed over the mouth) to create turbulence, and the mouth acts as a resonant chamber to enhance the resulting sound by acting as a type of Helmholtz resonator. Whistling can also be produced by blowing air through enclosed, cupped hands or through an external instrument, such as a whistle or even a blade of grass or leaf.