Scientists Build a Device That Splits Sound into a Rainbow

In the world of light, we’ve long had the prism—a timeless symbol of science, splitting white light into its constituent colors with elegance and precision. Now, thanks to a team of scientists in Europe, sound finally has its own version.

In a study recently published in Science Advances, researchers from the Technical University of Denmark and Universidad Politécnica de Madrid have unveiled a groundbreaking device called an acoustic rainbow emitter (ARE). Like a prism for sound, the ARE takes in a broadband white-noise signal—rich with many frequencies—and fans it out into a rainbow of pitches, sending each in its own direction through open air.

The result is something nature has long achieved but engineers have only dreamed of: a passive, electricity-free structure that can control sound with stunning finesse across a broad spectrum of frequencies.

Nature’s Blueprint: Ears That Sculpt Sound

Across the natural world, evolution has shaped ears into marvels of acoustic engineering. From the elegant folds of the human ear to the radar-like lobes of bats and the sonar systems of dolphins, living creatures have long been able to manipulate sound waves with passive biological architecture. They don’t need electronics or power sources—just cleverly sculpted surfaces.

This natural mastery of sound has inspired scientists for decades, but mimicking it in synthetic systems has proven remarkably difficult. Most human-made devices that manipulate sound rely on active electronics, like microphones or speakers, or on narrow-band resonance-based structures that work only at specific frequencies.

“Current acoustic systems have been able to split sound in closed environments, but they struggle to offer fully controlled, broadband manipulation of sound in free space,” explains lead researcher Dr. Romain Fleury from the Technical University of Denmark. “We wanted to change that—and we wanted to do it with nothing but passive materials.”

The Birth of an Acoustic Rainbow

At the heart of the breakthrough is computational morphogenesis, a cutting-edge design approach that combines evolutionary algorithms, structural optimization, and physics-based simulations to create forms that are both complex and functional.

The team used topology optimization—a technique that essentially evolves a design through trial and error, guided by precise performance goals. Their aim was clear: design a single, solid object that could take in omnidirectional white noise and scatter the various sound frequencies into different, predetermined directions. In other words, create an acoustic prism.

Using wave-based modeling grounded in the Helmholtz equation—a fundamental tool for describing sound propagation—the researchers simulated how sound waves would move and scatter through air around different structural shapes. They then 3D-printed the optimized designs in solid plastic and tested their performance.

The result? A football-sized object that can split a cloud of sound into directional threads—an acoustic rainbow born not from wires and power, but from pure geometry.

A Symphony of Sound Control—Without Electricity

Perhaps the most remarkable part of the ARE and its companion device, the lambda splitter, is that they function entirely through passive scattering. There are no moving parts, no batteries, and no active electronics. All they require is sound.

The ARE separates sound frequencies much like a prism splits white light. Meanwhile, the lambda splitter is engineered to take a mixed-frequency input and split it down the middle—sending high frequencies in one direction and low ones in another.

In both cases, it’s the precise shape of the plastic surface that does the work. When a sound wave strikes the object, some frequencies are deflected this way, others that way, all depending on how the shape has been mathematically crafted.

This type of design takes a page directly from nature’s playbook: passive control through form alone.

A Future Tuned by Geometry

While the devices may sound abstract, the implications are anything but. From sonar and radar to smart microphones, medical ultrasound, and even architectural acoustics, the ability to passively control sound with such accuracy is a leap forward.

For example, in sonar applications, splitting frequencies could allow a single underwater ping to scan in multiple directions at once. In hearing aids, it could help filter background noise with no added electronics. In speaker systems or concert halls, sound could be shaped and steered in new ways with sculpted surfaces alone.

“It’s not just about what sound is, but where it goes,” said Dr. Fleury. “We’re learning how to sculpt sound fields just by shaping materials. That’s incredibly powerful.”

This work also lays a foundation for future advances in wave-based sensing and control, including technologies that use electromagnetic waves, mechanical vibrations, or even water waves. The same design tools—computational morphogenesis and passive optimization—can be applied beyond sound to many other wave phenomena.

Echoes of Tomorrow

In a world increasingly powered by smart, sustainable systems, devices that can function without electricity are more than scientific curiosities—they’re essential building blocks. And the ARE is a shining example of how mathematics, physics, and biology can come together to shape a future of low-power, high-function wave control.

The researchers are already exploring further refinements—smaller devices, broader frequency control, and new materials that might bring these innovations into commercial applications. But even now, the ARE stands as a poetic intersection of science and sound.

A prism for the ear. A rainbow made of waves. And a new way of listening to the world—not with electronics, but with shape, silence, and design.

Reference: Rasmus E. Christiansen et al, Morphogenesis of sound creates acoustic rainbows, Science Advances (2025). DOI: 10.1126/sciadv.ads7497