Imagine being able to listen to your favorite podcast or song without disturbing others—without using headphones.
A team of researchers at Penn State has made a breakthrough in audio engineering that could make this possible.
They have developed “audible enclaves,” special zones where only the listener can hear sound, even if others are nearby.
Led by acoustics professor Yun Jing, the researchers created these private listening zones using two ultrasonic beams that meet at a specific point.
The sound is only heard at this intersection, creating a private listening experience for the person standing there.
“We use two ultrasound transducers paired with an acoustic metasurface,” Jing explained.
“These devices send out beams that bend and meet at a certain point. Only at that point can a person hear the sound—everyone else remains unaware.
This creates a privacy barrier for listening.”
The key to this technology is the acoustic metasurface, a special type of lens made with tiny structures that bend sound waves.
These lenses, 3D-printed by co-author Xiaoxing Xia from Lawrence Livermore Laboratory, direct the ultrasonic waves along a curved path until they meet. On their own, the beams are silent, but when they intersect, they create an audible sound only at that exact location.
To test their invention, the team used a dummy with microphones in its ears.
They measured the sound at different points along the beams and confirmed that it was only audible at the exact intersection point, proving that the “audible enclave” worked.
The researchers also tested the system in a regular room with normal background noise, showing that it could work in places like classrooms, cars, or even outdoors. “We basically created a virtual headset,” said researcher Jia-Xin “Jay” Zhong. “Inside the enclave, a person can hear sound meant only for them.”
Right now, the system can project sound about a meter away and at a volume similar to regular speaking (around 60 decibels). However, the researchers believe they can increase both the distance and volume by making adjustments to the ultrasound intensity.
This exciting development could change the way we listen to audio in shared spaces. In the future, we might have personalized sound zones in public places, allowing people to enjoy music, podcasts, or even phone calls without disturbing those around them.
Scientists are continuing to explore ways to refine and expand this technology, opening up new possibilities for private listening experiences.
