Researchers in Tokyo have put a new twist on the use of sound to suspend objects in air. They've used ultrasonic standing waves to trap pieces of wood, metal, and water – and even move them around.
Researchers have used sound to levitate objects in previous experiments, dating back decades. But that work has largely relied on speakers that were set up in a line to bounce sound waves off a hard surface.
The new experiment uses four speakers to surround an open square area that's about 21 inches wide. Four phased arrays use standing waves to create an ultrasonic focal point in that space, as the researchers explain in a video about their work.
That means that they generate a suspending force — which can then trap particles and objects in mid-air. The objects can be moved around by manipulating the waves.