Wild Ultrasonic Beam Tech Bends Sounds For Private Listening Without Headphones
A new invention has proven that audio can successfully be transmitted directly to a listener's ears without being audible to others around. Using ultrasonic waves beamed through a 3D-printed "metasurface" an audio bubble is formed at the intersection of those waves, potentially providing listeners personalized audio privacy without the need to don headphones. The possible applications for this technology are many, but making it practical is the next step.
Imagine sitting in your car or chilling in your media room and being able to enjoy your tunes without bothering people around you or be in a bubble where surrounding noise is cancelled. That is the idea behind "audio enclaves"—a unique sound technology made by a couple of researchers from Penn State University. In a nutshell, special projectors beam self-bending ultrasonic waves that only produce audible sound (be it speech, music, tones, etc.) at a pre-determined intersection point. Outside of that bubble would be pure silence.
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According to the published research, the audio enclave relies on ultrasonic waves to carry audio information. waves at this frequency is beyond human hearing ability, so they're essentially inaudible as they travel through the air. While most acoustic systems, like sound pressure in the air, build sound from every source added together in a generally linear fashion, the new system literally bends the rules. Two ultrasonic beams of different frequencies are projected from 3D-printed metasurfaces—they are normally silent, but when they intersect in space (ideally centered a few centimeters across the front of the listener's head), self-bending effects of the waves allow them to generate an audible frequency.
The key to the bending effects is due to the specially designed acoustic metasurfaces that bend waves at a specific point. Zhong Jia-Xin, post-doctoral researchers in acoustics at Penn State and one of the authors of the research, said that "We essentially created a virtual headset. Someone within an audible enclave can hear something meant only for them — enabling sound and quiet zones." At the moment, the setup is limited to projecting to audio at 60dB at about one meter away, but the team believes that boosting the power of the ultrasonic beams can increase the volume and range.
This advancement could see plenty of real-world applications in terms of personalized audio and privacy in public/private spaces. However, the lack of a truly dynamic way to focus and channel the waves (similar to autofocusing in a camera) limits users in a limited static location, preventing freedom of movement.
