[HN Gopher] 3D-printed device splits white noise into an acousti...
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3D-printed device splits white noise into an acoustic rainbow
without power
Author : rbanffy
Score : 219 points
Date : 2025-06-15 15:54 UTC (3 days ago)
(HTM) web link (phys.org)
(TXT) w3m dump (phys.org)
| GloamingNiblets wrote:
| 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
| ttoinou wrote:
| Thats crazy ! Thanks for sharing
| WJW wrote:
| That is a very wild shape indeed. I wonder if there is some
| analytical way to derive these or if some type of search
| algorithm will remain the best way.
| GloamingNiblets wrote:
| Given the elegance of the wave equation, I like to imagine
| there are solutions with some sort of symmetry and structure.
| We are unfortunately missing the tools and knowledge to find
| these solutions today!
| neuroelectron wrote:
| One more step toward building the pyramids.
| voidUpdate wrote:
| I mean we already built the pyramids...
| Cthulhu_ wrote:
| Yeah I'm not sure what the grandparent refers to. They're not
| mysteries or impossible to build, just labor intensive and
| expensive. Humanity has built bigger structures since then;
| skyscrapers, dams, underground complexes like the LHC,
| stadiums, bridges, cities (non-organically grown), etc.
| voidUpdate wrote:
| There are fringe theories that the pyramids were built
| using sounds to levitate the stone blocks, which are backed
| up with footage of ultrasonic acoustic levitation of
| polystyrene balls, and these days probably ai generated
| video too. Instead of using the Nile to transport them and
| ramps and rollers to lift them
| egypturnash wrote:
| 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
| catlifeonmars wrote:
| I'm wondering if you can change the shape in such a way that
| rotating one would produce an arpeggio.
| wizardforhire wrote:
| I'm game to do some heavy lifting if you're serious.
| aa-jv wrote:
| I'm in.
|
| Although I think this also has applications as a mechanical
| control mechanism, replacing expensive potentiometers with
| relatively cheaper 3D-printed parts. I've dreamed-up an
| optical/laser variant in my head a hundred times, fun to look
| at it in the audio domain.
| bobmcnamara wrote:
| Whoa it's like an ear but for light!
| recursive wrote:
| But for sounds
| ttoinou wrote:
| Seems like you are filtering the OP white noise broad band
| joke into a coherent explanation
| dtgriscom wrote:
| 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.
| _spduchamp wrote:
| I love corregated concrete! Those highly ordered early
| reflections can make a cool sound if you stand about a few feet
| away and clap your hands. I've wondered if it was possible to
| vary the bands to encode a designed sound in the reflection.
| Probably.
| ItCouldBeWorse wrote:
| Wait, so you could encode a forrests-leaves-swaying in the
| wind sound- into corrugated concrete?
| _spduchamp wrote:
| Not sure about that, but more like using Impulse Response
| techniques like in convolution reverb, to craft a short
| sound that reflects back given a burst of sound like a
| clap.
|
| For long sustained sounds using evenly space round rods can
| create sound with wind, like an Aeolean harp.
| zharknado wrote:
| 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?
| wahern wrote:
| Reminds me of Ben Underwood, the blind kid who used echo
| location around the house, playing basketball, riding his bike
| around the neighborhood, etc:
| https://www.youtube.com/watch?v=fnH7AIwhpik
| https://en.wikipedia.org/wiki/Human_echolocation#Ben_Underwo...
| literalAardvark wrote:
| https://en.wikipedia.org/wiki/Human_echolocation
|
| Bloody hell, I can't do all that...
|
| I wonder how they discovered that "clicking" works, seems so
| counterintuitive to discover. Though it's fair that I don't
| spend anywhere near that much time listening carefully and
| noticing how sharp sounds reflect.
| viraptor wrote:
| > I wonder how they discovered that "clicking" works
|
| I won't think it's they unexpected - have a walk a forest
| with loud insects. You'll hear a lot of interesting noises
| shaped a lot by what you stand near to. Large trees
| especially change how you hear things quite a lot.
| xattt wrote:
| Before practical applications, my first thought was a grade-
| school science fair entry. It's novel enough for judges not to
| have seen it for a couple of years.
| chrisweekly wrote:
| This is the kind of thing that keeps me coming back to HN more
| often than I should. So cool.
| bix6 wrote:
| How the heck do you arrive at such a crazy shape wow this is
| amazing.
| WJW wrote:
| 1. Start with a non-crazy shape that sort of does the same
| thing but worse (ie non-linearly or with big power fluctuations
| for different frequencies). Almost all shapes will interact
| with a sound wave in a frequency dependent manner so you can
| quickly scan through many initial options.
|
| 2. Define a goal function describing the desired outcome (like
| the "rainbow" shape of the linked article)
|
| 3. Permute the shape you started with iteratively with
| algorithms like simulated annealing, using the goal function
| from 2 as a means of defining the quality of the current
| solution.
|
| The actual scientific paper
| (https://www.science.org/doi/10.1126/sciadv.ads7497) is worth
| reading. The goal function is the "Figure Of Merit" (FOM),
| described in equation 1. They also make a two-prong version
| they call the "lambda emitter" that takes in a mix of sound
| frequencies and directs low and high-frequency sound waves in
| different directions.
| Onavo wrote:
| Solid state FFT?
| fellatio wrote:
| It would need to do something like spit out each frequency in a
| different direction then you use light material in circle that
| flaps when sound energy is transmitted in that direction.
| Sounds possible. Analog computer of sorts.
| WJW wrote:
| Do you mean a prism?
| ttoinou wrote:
| That does seem like witchcraft
| hinkley wrote:
| There are ways of telling if she is a witch
| Peteragain wrote:
| 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.
| amelius wrote:
| Cool, but I'd rather see a nicer shape, like a human cochlea,
| which also splits sounds into frequencies.
|
| Perhaps if they added some more constraints (e.g. on
| smoothness) they would end up with a shape like that.
| WJW wrote:
| It seems plausible that Mother Nature had to make some
| compromises when designing the cochlea, like how much easier
| it is to grow a (rather symmetric) cochlea than the weird
| shape from the article and maybe optimizing more for certain
| sounds than for others.
|
| 3d printers and search algorithms don't have that restriction
| and can directly optimize for optimal splitting and minimal
| acoustic losses.
| amelius wrote:
| But is allowing an irregular shape not more likely to get
| you stranded in a local optimum?
| viraptor wrote:
| Why? And why wouldn't you expect an irregular shape to be
| the global optimum?
| failrate wrote:
| IIRC it is an array of cilia of different sizes that filters
| sound into different frequencies in the human ear.
| alanbernstein wrote:
| A cochlea doesn't really spatially disperse the frequencies,
| though, right? Rather, the isolated frequencies are extremely
| localized within the coil, and the hearing receptors are each
| located at the one point where they need to be.
|
| This object is sort of an eversion of a cochlea. Perhaps it
| could be made with a "nice" shape, but I wouldn't assume so.
| xattt wrote:
| What sort of ML method would do shape optimization?
| voidUpdate wrote:
| Quite a lot could probably do it. Have it adjust
| positions/shapes of blocks placed in a virtual setting, have
| its fitness function be based off how split apart the
| frequencies are, press train and make a coffee. Sort of like
| this https://rednuht.org/genetic_cars_2/
| qoez wrote:
| It's not really machine learning, it's just optimization
| (optimize the space of shapes to create the desired filter).
| The paper doesn't call it ML either
| muxator wrote:
| Neat method. However, the frequency range for the device is
| 7600-13600 Hz: less than an octave.
| xattt wrote:
| Terrible! I was expecting at least a 7599-13601 Hz split.
| viraptor wrote:
| This is the first device of that kind. It's a research paper.
| The method described works. They weren't going for the limits
| of the technology here, but proving that it works. Others with
| different requirements of frequency ranges can create their own
| versions.
| sfink wrote:
| Ah, so you're pointing out that you could scale it up and down
| and stack them to convert white noise into chords? Cool!
| hinkley wrote:
| Make two of them mirror imaged to each other, and the middle
| of the audience hears the music in a different key than the
| wings.
| poulpy123 wrote:
| So it's like a prism for sound ?
| mhb wrote:
| Just like it says in TFA. Go figure.
| amelius wrote:
| 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?
| adornKey wrote:
| I think the ear relies more on resonance (unrolled it's like a
| stretched rubber triangle). The higher you go, the more it
| reacts on higher frequencies. This one here seems to just use
| passive reflection to get the effect.
| Leo-thorne wrote:
| 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.
| CommenterPerson wrote:
| 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?
| jrklabs_com wrote:
| 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?
| davidmurdoch wrote:
| 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
| fudged71 wrote:
| I can't find it now, but there was a youtube video of a guy
| building a fence to block road noise by building interlocking
| pottery 'bricks' with cavities that would absorb certain
| frequencies
| metalman wrote:
| helmholtz resonators, well known in acoustical engineering,
| also known as beer bottles and people, enough of which can
| significantly alter an acoustical signal. the idea of useing
| specific shapes to redirect sound is new to me, but parralels
| how reflected coulor can work in birds and insects, where two
| mechanisms are employed, pigments that simply absorb(heat up)
| with some frequencys and reflect others, and then mechanical
| structures that are tuned to capture some frequencys and
| reflect others, producing the iridesent effects that are so
| attractive. recent work has revealed that silk and artificial
| cloth's, can convert sound into heat quite effectivly, and
| other work where transparent plastic is put as an extra sound
| absorbing layer in windows
| antgiant wrote:
| This video? https://www.youtube.com/watch?v=y9-p4AkgVU8&pp=4g
| cMEgpwZXJwb...
| sbeckeriv wrote:
| Could you build this in to a decoder? A hidden message within the
| white noise and this filters to one or more frequencies?
| mensetmanusman wrote:
| I'm from the future and we use this technique with digitally
| planted corn seed to build 100000 km^2 diffractive concentrators
| to more effectively image near the center of the Earth.
| ttshaw1 wrote:
| >Unlike nature, which utilizes passive structures to shape sound,
| most artificial sound control systems require active devices or
| resonance-based systems.
|
| What's wrong with resonance-based systems? I have to wonder if
| their side lobes and frequency range would be better if they used
| resonance
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