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The Visual Patterns of Audio Frequencies Seen through Vibrating Sand

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Re: The Visual Patterns of Audio Frequencies Seen through Vibrating Sand

#21
post #17
post #4

It 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

Forgive 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?

You 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.

Re: The Visual Patterns of Audio Frequencies Seen through Vibrating Sand

#22
post #17
post #4

It 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

Forgive 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?

Yes, 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.

Re: The Visual Patterns of Audio Frequencies Seen through Vibrating Sand

#23
post #4

It 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

I'm a cs person and never encountered this in school. Is this taught in engineering? Typical course names?

"Physics".

Re: The Visual Patterns of Audio Frequencies Seen through Vibrating Sand

#25
post #12

I wonder what would happen if you designed a helmet that vibrated your brain like that? Maybe some frequency could tweak pleasure centers, etc?

I 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.

Re: The Visual Patterns of Audio Frequencies Seen through Vibrating Sand

#26
post #4

It 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

I'm a cs person and never encountered this in school. Is this taught in engineering? Typical course names?

System Analysis and/or Control System.

Re: The Visual Patterns of Audio Frequencies Seen through Vibrating Sand

#28
"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

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_'deco...

Re: The Visual Patterns of Audio Frequencies Seen through Vibrating Sand

#29

Here'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&i...

Here's a not very good example using hair and a car stereo (http://youtu.be/4s_lpBkdoNc)

Re: The Visual Patterns of Audio Frequencies Seen through Vibrating Sand

#30
post #8

I wonder if that could be done at scale with a massive art installation and marbles. Now that would be mind blowing to watch.

I'd love to see an enormous version of this harmonic motion demonstration.

(http://sciencedemonstrations.fas.harvard.edu/icb/icb.do?keyw...)

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