Acoustic tractor beam creates an ultrasound tornado for large-scale levitation

[Judi Lynn]

Michael Irving
January 24th, 2018

Levitation is no longer just the realm of magicians, with engineers dabbling in ways to suspend objects in midair using magnets, heat flow or sound waves. Unfortunately, it usually only works with particles or tiny objects, but scientists from the University of Bristol have developed a new "acoustic tractor beam" that can trap larger objects, possibly paving the way for contactless production lines or even human levitation.

In previous acoustic tractor beam designs, two ultrasonic speakers face each other across an open space. The ultrasound waves emitted by both speakers meet in the middle, and the perfectly aligned pressure from both directions can keep particles and other very light objects hovering in that meeting point (called the standing wave).

But there are a couple of problems with this technique that have limited the size of objects that can be levitated. If an object isn't positioned perfectly, the difference in pressure can cause it to whizz off out of the tractor beam, and if an object is larger than the wavelength of the sound waves, it will spin faster and faster until it, again, flies off.

The Bristol device was designed to counteract those issues by arranging a set of speakers in a bowl shape. These speakers produce sound in a rapidly spinning pattern, creating a kind of "sound tornado" with louder waves spinning around a silent core. That core acts like a 3D version of the standing waves produced in earlier acoustic tractor beams, keeping objects levitating motionless in the eye of the storm.

More:
https://newatlas.com/levitation-acoustic-tractor-beam/53120/

[Cracklin Charlie]

1. Flying cars, anyone?