POSTECH Built a Sound Laser to Beam Audio to One Person

Parametric acoustic arrays have spent years trying to focus sound like an optical flashlight, colliding high-frequency ultrasound waves in mid-air to produce an audible signal. The major bottleneck has always been hardware bulk: traditional setups rely on clumsy grids of dozens or hundreds of transducers, while vibrating diaphragms inevitably spill parasitic noise sideways like a rattling budget soundbar.

Engineers at POSTECH bypassed that hardware nightmare by creating MiPAL, a compact single-element speaker driven by 3D-printed metamaterials. Mounted directly on the front is an acoustic metasurface that functions like an optical lens, straightening uneven ultrasound waves into a razor-thin directional corridor.

On the back of the device, elastic meta-elements act as an acoustic firewall, absorbing unwanted structural vibrations and killing side-channel sound leaks. In simulated airplane cabin tests, the setup successfully delivered targeted audio across a frequency range of 500 Hz to 10 kHz—spanning more than four octaves—without spilling audible noise into neighbouring seats.

A personal audio bubble without shoved-in earbuds sounds like a dream for long-haul flights, right up until advertisers realize they can whisper targeted product pitches directly into unsuspecting skulls on the street.

Source: Nature