口哨，古称啸，是一种通过嘴内不断流过的空气发声的方法。空气流被舌头、嘴唇、牙齿或手指控制来产生湍流来产生声音。用手或者借助乐器哨子甚至是简单的树叶也可以叫口哨。

Whistling without the use of an artificial whistle is 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.