Acoustic levitation

Acoustic levitation (also: Acoustophoresis) is a method for suspending matter in a medium by using acoustic radiation pressure from intense sound waves in the medium.

Sometimes sound waves at ultrasonic frequencies can be used to levitate objects, thus creating no sound heard by the human ear, such as was demonstrated at Otsuka Lab, while others use audible frequencies. There are various ways of emitting the sound wave, from creating a wave underneath the object and reflecting it back to its source, to using a (transparent) tank to create a large acoustic field.