The Acme Siren is a percussion instrument used in concert bands for comic effect. Often used in cartoons, it produces the stylized sound of a police siren.
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.[1]
Acme is the trade name of J. Hudson & Co. of Birmingham who developed and patented the Acme Siren in 1895. It was sometimes known as "the cyclist's road clearer".[2]