Scientists Create "Audible Enclaves" That Can Curve Sound to One Crowd Member at a Time

Friday, 18 April 2025 00:58

With no headphones needed, ultrasound-based tech can beam audio through the air to a single person, even around obstacles.

Imagine you're in a crowd at a festival, concert museum or even a public square, and suddenly, you hear a message meant only for you. No headphones, just sound. That’s the promise of "audible enclaves," the byproduct of new technology developed by scientists and researchers at Penn State that could redefine how sound is experienced in public spaces.

Led by Jiaxin Zhong, a postdoctoral scholar in acoustics, and Yun Jing, a professor of acoustics at Penn State, the research team has figured out how to use ultrasonic waves to beam sound through the air to a single person without anyone nearby hearing a thing. They published their findings in the multidisciplinary scientific journal Proceedings of the National Academy of Sciences.

The tech works by overlapping two high-frequency beams that are silent to human ears on their own. But when they meet at a specific point in space, they generate a new frequency—the difference between the two—that falls within the audible range. That exact spot becomes a so-called "audio enclave," essentially a pocket of sound, and if you step outside of it, everything goes quiet.

The sound can also curve around objects to reach its destination. This is made possible by engineered "acoustic metasurfaces," which act like lenses for sound by bending the beams in precise directions. That means even if the listener isn’t directly in the line of sight, the message can still find its way to them.

"The self-bending ultrasonic beams created by acoustic metasurfaces, though inaudible, can bypass obstacles such as human heads," according to the study. "At their intersection behind obstacles, highly localized audible enclaves are formed due to the local nonlinear interactions."

To test the system, the team used a dummy with microphones inside its ears. Only when the figure's head was placed at the intersection point could the audio be detected, confirming that the sound was completely contained to that tiny zone.

The tech can create an audible enclave up to about three feet away, at a volume similar to everyday conversation. It’s still in the experimental phase, but the potential applications span everything from immersive art installations and museum exhibits to individualized experiences at live events. Even everyday environments like airports or libraries could benefit, offering directional audio without adding to the noise pollution.

You can read the team's findings here.