Scientists from the University of Bristol have boasted that they made the largest object in the history of the development of acoustic rays-attractors to levitate. And even if this is just a polymer ball with a diameter of 2 cm, they are already making plans to levitate a person. It's all about a new method called the "ultrasonic tornado".
Acoustic levitation using attractor beams works very simply. At a strictly defined distance, two sound emitters are installed, from which intersecting ultrasonic waves emanate. At this particular point in space, a standing wave is formed, within which the object can levitate.
The key word is "can" - you need to perfectly balance the characteristics of the target, otherwise the excess pressure from the acoustic waves will simply throw it away. Just this problem was solved in Bristol, where they built a bowl with emitters located around its circumference. When it works, the "sound pattern" looks like a swirling spiral or tornado - waves move around a fixed center in which an object levitates.
To prevent the ultrasonic tornado from spinning up and throwing out the object, the system is equipped with a mechanism for switching the direction of the waves, so that they alternate and compensate for the effect of each other. This approach made it possible to bypass the limitation on the size of the object - now it can be much larger than the wavelength, which opens up prospects for levitation of really large and useful objects in the household.