Acme siren

The Acme siren is a musical instrument often used for comic sound effects. Originally created by Acme Whistles in 1895, it produces the stylized sound of a police siren. It is one of the few aerophones in the percussion section.

The instrument is typically made of metal and is cylindrical. Inside the cylinder is a type of fan-blade which, when the performer blows through one end, spins and creates the sound. The faster the performer blows, the faster the fan-blade moves and the higher the pitch the instrument creates. Conversely, the slower the performer blows, the lower the pitch.