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.

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.

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?

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

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

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?

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

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

So it's like a prism for sound ?

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

That does seem like witchcraft

Solid state FFT?

One more step toward building the pyramids.

Whoa it's like an ear but for light!