Penn State researchers have developed a 3D-printed acoustic metasurface that turns ordinary speakers into highly directional audio devices capable of creating a tiny, private “sound bubble.”

Key Highlights:

• The thin, 3D-printed cover (about 6 inches in diameter) attaches to parametric array loudspeakers (PALs) and focuses sound into an extremely small, isolated spot — roughly the size of a stick of gum (slightly wider than 1 inch and less than 0.25 inches tall).
• Sound is clearly audible and high-quality only inside this precise focal point (about 4 inches from the speaker). Just 2 inches outside the spot, volume drops by up to 50 decibels.
• The system delivers excellent audio quality across both high and low frequencies, including deep bass down to 38 Hz — a major improvement over traditional directional audio tech.
• Unlike complex active systems, this metasurface is completely passive, low-cost, and easy to mass-produce with a 3D printer or plastic mold.

Potential Applications:

• Private listening in public spaces (ATMs, ticket kiosks, retail displays)
• Personalized audio in vehicles (multiple passengers listening to different content)
• Headphone-free audio without disturbing others

The research, led by doctoral candidate Jee Woo Kevin Kim and professor Yun Jing, was published in IEEE Transactions on Ultrasonics (May 2026).