Science news: "3D-printed device splits white noise into an acoustic rainbow without electricity"

[neRok]

3D-printed device splits white noise into an acoustic rainbow without electricity

In a study published in Science Advances, researchers from Technical University of Denmark and Universidad Politécnica de Madrid demonstrate a new device called an acoustic rainbow emitter (ARE) that takes in broadband white-noise signals from a point source that radiates sound equally in all...

phys.org

This sounds pretty interesting. I wonder if something could be devised and attached to the back wall that directs the bass waves away through a door or the ceiling etc?

There's a few comments about the article on HackerNews. One commenter says "The linked original paper is readable and answered many questions. They simply embrace the idea that some "crazy shape" will work, and then do "machine learning" in a simulation to find it."

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In a study published in Science Advances, researchers from Technical University of Denmark and Universidad Politécnica de Madrid demonstrate a new device called an acoustic rainbow emitter (ARE) that takes in broadband white-noise signals from a point source that radiates sound equally in all directions and scatters it up so that different sound frequencies or pitches are emitted.​

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Similar to how a prism splits white light into a rainbow, the ARE device steers each frequency in different directions, creating an acoustic rainbow.​

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Apart from the ARE, the researchers also designed a lambda splitter that takes in a mix of sound frequencies and directs low and high-frequency sound waves in different directions.​

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Both devices operate on the principle of passive scattering, where the acoustic system is purely driven by interactions between the hard plastic surface and sound waves, requiring no electricity. The rainbow emitter and the lambda splitter are excellent examples of how a smart arrangement of passive structures can be used to control sound without relying on energy-intensive resonance or active components.​

 

[RandomEar]

This sounds pretty interesting. I wonder if something could be devised and attached to the back wall that directs the bass waves away through a door or the ceiling etc?

Technically, this has been possible for a long time. You just need a good solver and lots of computational power to optimize the shape of your object(s) for a broader range of wavelengths.

The main problem here would be the required size: At 50 Hz, your wavelength is 6.86 m. Assuming you need something on the order of half a wavelength to redirect those waves, you've got a room size problem. Even at a quarter wavelength you're running into the same limits around 35 Hz. So this isn't really feasable for regular rooms, but it might be interesting for concert halls and such. In the Elbphilharmonie they did implement a similar technique to design a concert hall without bad seats (from an acoustics standpoint). The wall panels are each individually calculated and contain dozens of "acoustic lenses".