Acoustic Levitation — Water Droplet Suspended in Sound
128.32 £
A water droplet levitated by acoustic radiation pressure in a standing wave node — the droplet’s shape flattened by the acoustic pressure into an oblate spheroid, suspended without physical support between two acoustic transducers.
Description
Acoustic levitation uses the radiation pressure of standing sound waves to suspend small objects at the nodes of a standing wave pattern — the points where the acoustic pressure is at minimum and the acoustic radiation pressure creates a stable equilibrium trapping objects. This laboratory setup uses two facing ultrasonic transducers operating at 22kHz (above human hearing) with a precisely controlled separation that creates standing waves with nodes every 7.7mm. A water droplet of approximately 3mm diameter is shown at one of these nodes, its shape flattened from a sphere to an oblate spheroid by the acoustic pressure field. Shot at 1/4000 second under studio lighting against a dark background, the droplet’s spherical reflections and the water surface tension behaviour are clearly visible. The levitating droplet appears to violate gravity — a physical phenomenon made visible through photography.
