In recent research published in *Proceedings of the National Academy of Sciences*, Professor Yun Jing from Penn State College of Engineering and his team have successfully created an “audible enclave”—a localized sound zone where only a listener can hear sounds, effectively isolating them from nearby individuals even within shared spaces like cars or when standing close to the source.

The researchers achieved this effect by utilizing two ultrasonic transducers paired with acoustic metasurfaces to emit nonlinear ultrasound beams that converge at a single point, creating an area accessible solely to someone positioned there. This generates an invisible barrier for private listening experiences.

Essentially, these two ultrasound beams remain silent until they interact nonlinearly upon intersection, producing audible sound waves undetectable by others because the obstacles—such as human heads—bypass them directly towards their designated meeting points.

Testing in a standard room demonstrated multiple reflections and echoes within the space, suggesting potential applications across diverse environments including classrooms, vehicles, or outdoor settings.

The experience inside an “audible enclave” is akin to wearing virtual headphones with exclusive audio content; current tests demonstrate transmission of up to 60 decibels of this "exclusive sound" over a distance of one meter within the zone. Further increasing ultrasonic intensity could potentially extend both the transmission range and volume.

This technology shares similarities with the “Secret Sound Transmission” ability often depicted in martial arts novels or dramas, where advanced practitioners can transmit sounds across greater distances at higher volumes.
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