Researchers have developed a 3D-printed device that does for sound what a prism does for light – splitting a single input into distinct components. Called the acoustic rainbow emitter (ARE), the invention takes a burst of white noise from a single miniature speaker and separates it into different pitches. Remarkably, it requires no power, motors, or microchips – only precision geometry.
The ARE was generated using computational morphogenesis, a design process where an algorithm reshapes a virtual structure, tests its acoustic response, and adjusts the shape through thousands of iterations. The final design resembles a complex labyrinth, guiding sound waves between 7.6 kHz and 12.8 kHz – a range spanning from kitchen timer beeps to ultrasonic dog whistles. The finished object, printed in rigid plastic, measures just 10 centimeters across and fits comfortably in the palm of a hand.
So, how does it work? Imagine sound waves as runners starting at the same time but taking different routes. Inside the ARE, angled walls send each frequency along a unique path. By the time the sound exits, the waves are out of sync. Some reinforce one another in specific directions, while others cancel each other or scatter, creating a 360-degree “acoustic rainbow.” For example, lower frequencies beam northeast, while higher frequencies veer southwest.
Because the ARE uses passive scattering, it avoids the energy loss and narrow frequency ranges typical of traditional resonant devices. Using the same technique, the research team also built a “lambda splitter” that sends low notes left and high notes right, proving the method can be tailored for different audio functions.
Though still a prototype, the ARE hints at a future of battery-free speakers, directional sensors, and hearing aids that can shape and steer sound with elegant simplicity.