Siren

Siren, wood and metal, London, 1870.

Built by London-based instrument maker William Ladd, this siren was designed by Charles Cagniard de la Tour in 1819.

Originally developed to measure the number of vibrations of a body in a given time, Cagniard’s siren was the first artificial sound source with a frequency that varied depending on the speed of rotation. The siren worked by pushing in pressurised air through a cylindrical cavity (most likely coming from a wind chest and bellows under it) through two discs. The faster the disk rotates, the higher the sound. The number of turns was registered on the dials that sit on top of the siren indicating the number of vibrations per second. It is said Cagniard named its siren because of the object’s ability to produce sound underwater (when water is pushed in as opposed to air), evoking the chants of mythical Greek sirens luring sailors to death.