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The Visual Patterns of Audio Frequencies Seen through Vibrating Sand
- TheRubyist 13y agoNo.
- joeblau 13y agoThey have this at the Exploratorium! Definitely cool to play with.
- Jabbles 13y agoIt is interesting, but it's a standard way of demonstrating normal modes, or the applications of eigenvectors. I would think most physics and engineering undergraduates have studied this. That's not to say you shouldn't watch it, but just to put it in perspective - this is a topic studied in the 1st/2nd year of university, not a poorly-understood topic for research. https://en.wikipedia.org/wiki/Normal_mode https://en.wikipedia.org/wiki/Normal_mode
- jstanley 13y agoIs this essentially the same as a standing wave, except 2-dimensional?
- leephillips 13y agoYes, the sand settles into the nodal lines of the pattern of vibration on the plate; those are the places where the plate is not moving. The same frequencies on a circular plate will produce different patterns.
- throwaway1979 13y agoI'm a cs person and never encountered this in school. Is this taught in engineering? Typical course names?
- btilly 13y agoAs a math person, I look at this and think "Fourier series". I encountered the ideas in both Classical Mechanics 1 (third year physics course where I took it) and Differential Equations (third year math course where I took it). It is still a nice visualization.
- diydsp 13y agoIt's very close to Fourier series, but since the "solutions" (the equilibria) are not integer multiples of a fundamental, but solutions to a 3-dimensional wave equation, it's more like "wave equation."
- btilly 13y agoFrom a mathematician's point of view it is a Fourier series. You have the property that any starting state can be divided into the sum of orthogonal components. No matter how complex the components are, that's still a Fourier series. A physicist would disagree, I am sure. But to a mathematician, an orthonormal wavelet basis is also a Fourier series.
- leephillips 13y ago"Physics".
- ndr 13y agoSystem Analysis and/or Control System.
- mcphage 13y agoForgive my ignorance, but I don't have a physics or engineering background. Given it's a well understood phenomenon, is there some way of generating mathematically what the patterns will be for a given plate shape and frequency?
- leephillips 13y agoYou solve the wave equation, a differential equation for the small-amplitude motion of the surface. The solutions depend strongly on the shape of the boundary, as is usually the case. For some shapes the patterns can be found analytically. For more complicated boundaries it's not too hard to solve this equation numerically - it's linear. Orders of magnitude easier than, say, calculating the flow of water down a pipe.
- stephencanon 13y agoYes, the shapes can be predicted by numerical solution of the governing PDE. I don't think that's what you had in mind, however. For an arbitrary plate shape, the solutions do not generally have what you might think of as a nice closed-form expression. For certain specific cases (like a square plate), these modes do have reasonably tidy descriptions.
- n3rdy 13y agoCouldn't you use something like this on a small scale to implement a better random number generator for computers? Looks like all it would take is a tiny speaker, a thin metal plate, and something that reads that metal plate like a QR code. The tone could then be randomized by a psuedo-random number generator, and even though the shapes generated are similar, they are never quite identical.
- masnick 13y agoBold title for WWDC day.
- leephillips 13y agoBecause some shiny new gadget will impress you more than a beautiful visualization of the mathematical structure of nature?
- masnick 13y agoThat was tongue-in-cheek (mostly...you never know with WWDC). This video reminds me a bit of A New Kind of Science (http://en.wikipedia.org/wiki/A_New_Kind_of_Science http://en.wikipedia.org/wiki/A_New_Kind_of_Science): some of the phenomena Wolfram discusses gave me the same "holy! how does this happen in nature" kind of reaction.
- leephillips 13y agoSorry for coming on so strong. And for being that guy who misses the tone.
- masnick 13y agoNo worries, we're all that guy sometimes. +1 for emoji support in HN comments. (Also ironic...mostly.)
- deleted 13y ago[deleted]
- ColinWright 13y agoThe mods have changed the title, so your comment makes less sense now. For those who are confused, the original title was something like "This is the best video you'll ever see!" or similar.
- ck2 13y agoI wonder if that could be done at scale with a massive art installation and marbles. Now that would be mind blowing to watch.
- DanBC2 13y agoI'd love to see an enormous version of this harmonic motion demonstration. (http://sciencedemonstrations.fas.harvard.edu/icb/icb.do?keyword=k16940&pageid=icb.page80863&pageContentId=icb.pagecontent341734&state=maximize&view=view.do&viewParam_name=indepth.html#a_icb_pagecontent341734 http://sciencedemonstrations.fas.harvard.edu/icb/icb.do?keyw...)
- swamp40 13y agoI wonder what would happen if you designed a helmet that vibrated your brain like that? Maybe some frequency could tweak pleasure centers, etc?
- reirob 13y agoWondering if this actually happens when we are listening to music? ;)
- leephillips 13y agoI don't think small deformations of the brain do much, because they don't change the connectivity or electrical activity of the neurons. However, there are devices that induce currents inside the brain by applying magnetic fields, and this has profound effects.
- ccallebs 13y agoHas this been attempted in a zero-gravity environment (or even water)? Would that completely obliterate the results of the test, as the sand wouldn't be on a solid surface? I'm curious what the results would be.
- maeon3 13y agoThe image created by the vibrations and sand reminds me of the Probability densities corresponding to the wavefunctions of an electron in a hydrogen atom. Link to Image: http://en.wikipedia.org/wiki/File:HAtomOrbitals.png http://en.wikipedia.org/wiki/File:HAtomOrbitals.png
- iknowno_one 13y agoHere's a Science Friday video of the same thing but without the music on top, so you can actually hear the frequencies. http://www.npr.org/player/v2/mediaPlayer.html?action=1&t=1&islist=false&id=103210918&m=103221404 http://www.npr.org/player/v2/mediaPlayer.html?action=1&t=1&i...
- DanBC2 13y agoHere's a not very good example using hair and a car stereo (http://youtu.be/4s_lpBkdoNc http://youtu.be/4s_lpBkdoNc)
- sambeau 13y ago"The study of the patterns produced by vibrating bodies has a venerable history. One of the earliest to record that an oscillating body displayed regular patterns was Galileo Galilei. In Dialogue Concerning the Two Chief World Systems (1632), he wrote: As I was scraping a brass plate with a sharp iron chisel in order to remove some spots from it and was running the chisel rather rapidly over it, I once or twice, during many strokes, heard the plate emit a rather strong and clear whistling sound: on looking at the plate more carefully, I noticed a long row of fine streaks parallel and equidistant from one another. Scraping with the chisel over and over again, I noticed that it was only when the plate emitted this hissing noise that any marks were left upon it; when the scraping was not accompanied by this sibilant note there was not the least trace of such marks. " http://en.wikipedia.org/wiki/Cymatics http://en.wikipedia.org/wiki/Cymatics These patterns are also drawn on tiles in the Rosslyn Chapel and are thought to be displaying music: http://en.wikinews.org/wiki/Rosslyn_Chapel_music_score_'decoded' http://en.wikinews.org/wiki/Rosslyn_Chapel_music_score_'deco...
- ja27 13y agoWhy is it sometimes asymmetrical vertically? Is it just a slight variation where the plate isn't perfectly square or the bolt not in the exact center?
- gliese1337 13y agoIt appears to be simply a lack of sufficient sand to show all of the lines- some of them become symmetrical when more sand is sprinkled on.
- jtheory 13y agoInteresting, but for a similar experiment that's rather higher on the "cool" spectrum, check some of the videos with "oobleck" (non-newtonian fluid, like cornstarch and water) on an amp.
- jtheory 13y agoHere's the first one I saw, a couple of years ago: http://www.youtube.com/watch?v=Yp1wUodQgqQ http://www.youtube.com/watch?v=Yp1wUodQgqQ Linking it here because I just went searching for new examples, and none of what I found was quite as good at fooling my brain that living creatures were crawling out of the muck...
- jpenny_im 13y agoif you want to see many other examples, search for "chladni plate"
- ktf 13y agoThere's a really fun exhibit at the Exploratorium in SF that demonstrates this. Not quite so fancy, but if you can shove some kids out of the way it's still pretty cool to play with!
- jlengrand 13y agoActually, this is salt.