Ultrasonic sound waves have been used to levitate objects in crowded rooms to make hologram-like displays. Such acoustic levitation was previously only practical in empty spaces, but a new algorithm can quickly readjust the sound waves when they encounter an obstacle to keep the object in the air. Sound waves are comprised of air particles moving together. If manipulated in the right way, they can pick up and move objects. However, if the sound waves run into some other object that reflects or scatters them, the levitating object can come tumbling down.
Researchers at University College London previously used sound to levitate glowing beads to create floating 3D shapes. Now, they have developed a computational technique that enables them to levitate and manipulate objects above bumpy surfaces and near objects. They used 256 small loudspeakers arranged in a grid to levitate objects with precisely shaped ultrasound waves. When these sound waves encountered objects that would usually scatter them, like a wall or a houseplant, a computer algorithm quickly adjusted their shape to maintain levitation.
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