Penn State researchers printed a passive plastic lens that sits on a directional ultrasonic speaker and focuses sound into a pocket roughly the size of a fingertip, with no electronics and no power — though it only works with a parametric array loudspeaker, a niche ultrasonic…
Picture a person dancing in a quiet room with no speaker in sight and no headphones on. The music lives in a pocket of air about an inch across, somewhere above an empty shelf. That is the scene at the heart of a new acoustic device from Pennsylvania State University: a 3D-printed plastic cover that sits over a directional ultrasonic speaker and bends the sound the way a magnifying glass bends light, focusing it into a focal point slightly wider than an inch wide and less than a quarter inch tall.
The cover, reported by New Atlas on June 14, 2026, was developed by Jee Woo Kevin Kim and colleagues at Penn State and is described in a paper published in IEEE Transactions on Ultrasonics (DOI: 10.1109/TUSON.2026.3689544). It has no electronics and no power supply of its own; the geometry of the printed plastic does all the work, refracting the speaker's output into a focal point slightly wider than an inch wide and less than a quarter inch tall at a fixed distance from the device.
The cover is a passive acoustic metasurface — a thin structured material that manipulates waves using geometry alone. It is designed to work with parametric array loudspeakers (PALs), a specialized type of speaker that generates an ultrasonic carrier to project an audible beam. Without a PAL driving it, the cover does nothing. With a PAL array, the metasurface shapes and confines that already-directional beam into a tighter focal zone.
The mechanism is acoustic lens design in its most direct form. "To develop an acoustic metasurface, we use a large surface that works like a lens focusing a beam of light," said Yun Jing, professor of acoustics at Penn State and corresponding author on the paper. "The surface modulates sound waves in such a way that they converge at a central point after leaving the speaker, allowing us to focus the audio into a precise area."
The focal point forms approximately four inches from the speaker surface. When a microphone moved just two inches — less than the width of a credit card — away from the center of the focal point, volume dropped by roughly 50 decibels, about the difference between background music and a whispered conversation. The metasurface itself is roughly six inches in diameter, about the size of a small plate.
PALs are the established technology for sending a narrow column of sound to one listener in a gallery, a kiosk, or a trade-show booth. Kim's framing, as carried in the New Atlas summary, treats PALs as the reference point and a known compromise. Beams from a PAL reflect off walls and hard surfaces, scattering into the rest of the room. PALs also struggle to reproduce low frequencies, since the ultrasonic carriers they rely on do not deliver much bass. The printed cover is positioned as a low-cost, passive complement to that family, not a replacement for it.
The honest limits sit on the same page. The cover is a passive element, which means it still needs a PAL driver to generate the ultrasonic beam that the metasurface then shapes. A conventional speaker — a phone, a bookshelf speaker, or a Bluetooth unit — does not produce that carrier and cannot drive the cover. The focal geometry is fixed by the print, not electronically steered, so the listener has to sit in the right spot. The metasurface also faces frequency-response constraints at the low end, though Penn State reports the system demonstrated effective projection down to 38 Hz.
Two settings make the device's promise concrete. In a shared apartment, a person could keep listening after a roommate has gone to sleep, with the music confined to a small zone rather than radiating through the wall. In a small office or a library carrell, one workstation could receive its own audio without bleeding into the next desk. Kim has noted that commercial production could be as simple as 3D printing the component or using a plastic mold.
For hearing-aid users and listeners who are sensitive to sensory overload, a tight acoustic pocket is a real accessibility gain — though it is a use case to test rather than a marketed feature.
What to watch next is the primary source. The IEEE paper itself will provide the full methodology, the precise focal-point measurement plots, and the frequency-response curves. A first-party quote from Kim or Jing on the design intent and the low-end performance claim would complete the picture.