Penn State researchers have created ‘audible enclaves’ using ultrasonic beams, enabling listeners to hear sound privately without disturbing others. This innovative technology has the potential to transform personal audio experiences in various environments.
Imagine listening to your favorite podcast or music without headphones and without bothering those around you. This vision is closer to reality, thanks to a breakthrough by a team of researchers at Penn State.
Yun Jing, a professor of acoustics in the Penn State College of Engineering and the corresponding author of the study, and his team, have pioneered a new audio technology that creates “audible enclaves” — localized pockets of sound where only the intended listener can hear the audio. This innovative approach could revolutionize how we experience private listening in public or shared spaces.
In a study published in the Proceedings of the National Academy of Sciences, the researchers detail how they used two nonlinear ultrasonic beams to generate these audible enclaves. By directing these beams to intersect at a specific point, sound becomes audible only at that intersection, creating a unique privacy barrier for the listener.
“We use two ultrasound transducers paired with an acoustic metasurface, which emit self-bending beams that intersect at a certain point,” Jing said in a news release. “The person standing at that point can hear sound, while anyone standing nearby would not. This creates a privacy barrier between people for private listening.”
The technology leverages advanced acoustic metasurfaces — 3D-printed acoustic lenses with intricate microstructures that bend sound waves. These metasurfaces, developed by co-author Xiaoxing Xia, a staff scientist at Lawrence Livermore National Laboratory, enable the beams to follow a crescent-shaped path until they intersect.
Caption: By positioning metasurfaces in front of two ultrasonic transducers, dual ultrasonic waves travel at two slightly different frequencies along a crescent-shaped trajectory until they intersect, forming an audible enclave where sound cab be heard. At other points along the trajectory, sound is not heard — meaning private listening is possible.
Credit: Provided by Heyonu Heo/Penn State
To verify their system, the team used a dummy with microphones in its ears, replicating human auditory perception along the ultrasonic beam path.
“We confirmed that sound was not audible except at the point of intersection, which creates what we call an enclave,” added Jia-Xin “Jay” Zhong, a postdoctoral scholar in acoustics at Penn State.
Remarkably, the researchers demonstrated that their system works in common environments with typical sound reverberation, such as classrooms, vehicles or outdoor spaces. This versatility hints at wide-ranging applications, from quiet zones in open offices to recreational use in public areas.
“We essentially created a virtual headset,” Zhong added. “Someone within an audible enclave can hear something meant only for them—enabling sound and quiet zones.”
Currently, the system can transmit sound to a point about a meter away at a volume similar to conversational speech (around 60 decibels). The team believes they can enhance both range and volume by adjusting ultrasound intensity, broadening the technology’s potential use cases.
This pioneering project received support from the U.S. National Science Foundation and Lawrence Livermore National Laboratory’s Lab Directed Research and Development Program.
Source: Penn State University