Sound has remarkable effects on the human mind. It can delight us, scare us, depress us and uplift us.

But now, for the first time, physicists have shown that it can uplift physical objects too - in this case, a five centimetre polystyrene ball - using a principle called 'acoustic levitation'.

A team of researchers used three ultrasound transducers - which convert electric current into ultrasonic waves - to create a acoustic levitation device capable of hovering the ball in mid-air, about 7mm away from external surfaces.

Similar devices have previously levitated much smaller objects, but this is the first time that the technique has been used something something so large.
Fixed position

The team, split between the University of São Paulo in Brazil and Heriot-Watt University in Edinburgh, accomplished the feat by creating a standing wave between the transducers and the ball.

The shaping of the transducers into a tripod helped, too - providing greater stability.

"At the moment, we can only levitate the object at a fixed position in space," said Marco Andrade, who worked on the research. "In future work, we would like to develop new devices capable of levitating and manipulating large objects in air."

Eventually, it's hoped that the technique could be used for handling and manipulating very hot or hazardous materials.

It could also be especially handy in space, where lower surface tension of liquids in microgravity means droplets are bigger and not so easy to handle.

The research was published in the journal Applied Physics Letters. Image credit: Andrade et al, AIP Publishing.