Researchers Develop Technology That Delivers Sound Only to Specific Listeners

Industry News

Mar 20

Ever been annoyed by someone else’s music in a shared space or struggled to have a private conversation in a busy office? Researchers at Penn State University may have just solved these common issues with a breakthrough that creates “sound bubbles” — localized audio spots that only the intended listener can hear.

How Audible Enclaves Work

Penn State researchers developed what they call “audible enclaves,” a method that directs sound to a precise location without being heard by those nearby. This technology combines ultrasound waves with acoustic metasurfaces — specially designed materials that shape sound paths.

The system emits two ultrasound beams that travel along curved paths. These beams are silent on their own, but when they intersect at a specific point, they generate an audible sound wave that can only be heard at that precise location.

By carefully designing the ultrasound beams to bend around obstacles — like a person’s head — researchers ensured the sound reaches only the intended listener. This creates a “virtual headset,” providing private audio without headphones.

*(Credit: Provided by Heyonu Heo/Penn State)*

Overcoming Audio Challenges

Containing sound without physical barriers has long been a challenge due to sound waves’ tendency to spread as they travel. This is why conversations often carry across rooms and why traditional speakers fill spaces with sound.

Unlike existing directional sound systems, Penn State’s technology demonstrated effectiveness across a broad frequency range — from 125 Hz to 4 kHz — which covers most frequencies needed for speech and music. The system’s compact size is also impressive, with researchers achieving results using a source aperture just 0.16 meters wide.

*Jia-Xin “Jay” Zhong, a postdoctoral scholar of acoustics at Penn State, used a dummy with microphones in its ears to measure the presence or absence of sound along an ultrasonic trajectory.* ***(Credit: Poornima Tomy/Penn State)***

Real-World Applications

This breakthrough has significant potential across multiple environments. Museums could provide personalized audio guides without headphones. Libraries could offer students audio resources without disturbing others. In cars, passengers could enjoy individual sound zones while the driver listens to navigation instructions. Offices may also benefit from this innovation by creating private conversation zones without sound leakage.

Beyond convenience, this system could even help manage noise levels. Hospitals could maintain designated quiet zones while allowing important communication to continue in other areas.

Looking Ahead

While this technology offers exciting possibilities, there are still challenges to address. Converting ultrasound into audible sound requires high-intensity fields, which can be energy-intensive. Additionally, some distortion may occur when transmitting complex audio content. Researchers are exploring solutions like improved signal processing to enhance sound quality.

Though still in development, Penn State’s audible enclave technology presents a promising solution for delivering precise, private audio without the need for headphones. As researchers continue to refine the system, this innovation could change how sound is experienced in public spaces.

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