Whistling

Whistling by people can be done without a whistle. Hard to describe, it is done 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, curled tongue, teeth or fingers (placed over the mouth).

A very clear example of the way the lips look as whistling is happening

Another way to whistle; a similar method is to use only two fingers, one each side

The use of pursed lips, tongue and sometimes fingers is to create turbulence The curled tongue acts as a resonant chamber, acting as a type of Helmholtz resonator. The art of whistling is a hard task to accomplish but is much easier once mastered.

Whistling is done to make people at a distance hear your signal. Sometimes used to call a cab, it can be used in dense forest or on hill-tops. It is a non-verbal method of communication which says, in effect, "take notice, I'm here". Whistling is widely used by shepherds to control their dogs.