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Researchers harness ultrasound to create isolated pockets of sound only you can hear in a crowd | The key is intersecting ultrasonic frequencies to produce audible sound
Directing sound to a specific location is difficult because of how sound waves behave. As vibrations move through the air, they spread out, especially at lower frequencies....
To achieve total sound isolation, researchers from the University of Pennsylvania and Lawrence Livermore National Laboratory used ultrasound and nonlinear acoustics to "bend" soundwaves to produce audible vibrations that occur only at a specific location. Using acoustic metasurfaces, the researchers can control the path of ultrasonic vibrations, effectively curving the beams around obstacles and allowing them to intersect at a specific point. By precisely controlling the phase of the ultrasound waves, we create curved sound paths that can navigate around obstacles and meet at a specific target location."
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