In the late 80s I worked in a low cluster of buildings, each of which was topped with a band of vertical ridges spaced about 4" apart (sort of like a corrugated roof, but with vertical corrugations). One day a thunderstorm came through, and we discovered that the pulses of thunder, when they hit the corrugations, reflected as a quickly falling tone. The corrugations were working as an acoustic diffraction grating, with different frequencies reflecting in different directions.

Could you build this in to a decoder? A hidden message within the white noise and this filters to one or more frequencies?

Very neat, this reminds me of the organic shapes of passive demultiplexers in photonics such as https://pubs.acs.org/doi/10.1021/acsphotonics.7b00987

Kef has a "metamaterial" they add to their speaker drivers to absorb specific frequencies in order to modify the frequency response curve of the drivers themselves, as opposed to only trying to correct via the cabinet. https://us.kef.com/pages/metamaterial

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.

Brainstorming applications of knowing your angle relative to a point source:

- adaptive sports for visually impaired players like beep baseball?

- robot swarm members knowing their relative 2d position with a single microphone? (frequency for angle, amplitude for distance)

- a cheap, durable way for human workers to track the rotation cadence of slowly rotating machinery?

Neat method. However, the frequency range for the device is 7600-13600 Hz: less than an octave.

okay who wants to build a musical instrument that works by beaming white noise at a bunch of these things, with some way for the user to rotate them quickly and accurately

Can it be scaled up and done in reverse to create a point source of coherent audio from multiple speaker components covering different frequency ranges?

I'd like to passively divert annoying or redundant airport announcements down the drain.

More seriously, great concepts for architects to scale up and control noise?

This is the kind of thing that keeps me coming back to HN more often than I should. So cool.

I used to think you had to rely on circuits or resonance chambers to split sound frequencies, so seeing this done with a 3D-printed structure really changed how I think about it.

It made me realize how little design attention we actually give to sound. Most of the time we just passively listen, without thinking about shaping the path of sound. If structures like this can be made smaller and more portable, I can see a lot of interesting use cases in phones or compact voice-controlled systems.

Is this similar to how the human ear turns signals into frequencies?

I suppose the thing is linear? So it behaves like a Fourier transform?

One more step toward building the pyramids.

How the heck do you arrive at such a crazy shape wow this is amazing.

So it's like a prism for sound ?

Solid state FFT?

That does seem like witchcraft

Whoa it's like an ear but for light!