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Topic: OT: A sound physics lesson

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  1. #1
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    OT: A sound physics lesson

    Thought this was really cool and should interest many around here.

    http://youtube.com/watch?v=ToLI7WHOb...related&search=

  2. #2
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    Re: OT: A sound physics lesson

    Quote Originally Posted by EricWatkins
    Thought this was really cool and should interest many around here.

    http://youtube.com/watch?v=ToLI7WHOb...related&search=
    Amazing. I'm wondering:

    Do interesting things continue to happen well above the human hearing range? They don't show that....

    How would the behavior of say, sand, differ?
    What about flour?

    What if the same test was performed with various combinations of tones? Say two simultaneous sweeps that are always and octave apart? Always a fifth? Always and minor second?

    If there is a strict pattern for the specific resonant frequencies, will their overtones always make patterns that interfere with the fundamental to create a new pattern, or not? Will more dissont intervals create more intricate patterns, or will it quicky reach chaos?

    Thanks for the link!

    Belbin

  3. #3
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    Re: OT: A sound physics lesson

    Yeah, I was pretty fascinated myself. My brother sent me the link and he was telling me that many of the patterns were seen in ancient writings and that no one used to know what the symbols were. Pretty cool.

  4. #4

    Re: OT: A sound physics lesson

    I think that the salt (or sand or flour) doesn't make much difference. The key is the metal plate and how it resonates. If you choose a different size, thickness, shape or material, it will resonate at different frequencies and in different patterns.

    If you watch the video again, you can hear just when the patterns are ready to emerge. You hear the sound get louder and harsher as the plate starts to resonate, and then the salt suddenly shifts.

    The patterns really have a magical quality, don't they?

  5. #5
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    Re: OT: A sound physics lesson

    Quote Originally Posted by EricWatkins
    Yeah, I was pretty fascinated myself. My brother sent me the link and he was telling me that many of the patterns were seen in ancient writings and that no one used to know what the symbols were. Pretty cool.
    I was also wondering about whether there were any connections between what we saw there and "primitive" man's art and such. Betcha Joseph Campell would have a field day. It just seemed like too much to bite off so early in the thread. Thanks for mentioning that. I also wondered how much golden ratio we'd see in it....then I got spaced out and forgot about that. Any Fibonacci Geeks out there care to comment?

    Jon: You're probably right. but it would be cool to see some variables introduced.

    Belbin

  6. #6

    Re: OT: A sound physics lesson

    Very unusual and amazing. Natural phenomenon are so unpredictable.

    Thanks for that link.

    Ok that the salt (or sand or flour) doesn't make much difference.

    But what would happen with flour, water and levain ?

    SergeD

  7. #7

    Re: OT: A sound physics lesson

    I want to see it done with Jello. Imagine all the wonderful wiggles!

    Very cool, thank you for sharing!

  8. #8

    Re: OT: A sound physics lesson

    Definately cool stuff. There are secrets asscociated with that such as keys to understanding a lot of ancient texts and drawings.
    P4 3.0, 2 gig ram, nvidia 6800gt, 3 SATA drives, EMU-1820M, UAD-1, Studiologic SL-110, Mackie Universal Controller, Behringer Truth B2031A, Cubase SX3, Kontakt2, EWQL Gold, EWQL Choirs, EWQL Collosus, NI Akoustik Piano, NI Elektrik Piano, NI B4 II, EZ Drummer, Lyrical Distortion 1+2, Scarbee Bass, Real Guitar2, Atmospheres, Absynth1, GPO

  9. #9

    Re: OT: A sound physics lesson

    Quote Originally Posted by belbin
    How would the behavior of say, sand, differ?
    What about flour?
    Shouldn't make a difference.

    Picture gently damping a guitar string at its midpoint, and then plucking the string... as expected, you will hear a harmonic generated at twice the frequency of the open string.

    Getting (very gently) into the "wave mechanics" behind that familiar phenomenon, what you have, where your finger was, is a "node" -- a point on the string that does not move at all, while every other point along the string is moving up and down (now twice as fast as they would if the string were open, since you halved the vibrational length of the string with your finger).

    A "node" on a two-dimensional object (like a string) is a single point.


    -----------------------


    Suppose, instead of a string, the vibrating object is a two-dimensional object -- a flat surface of some sort.

    If you then "drive" that two-dimensional object (either by blasting a loud sine wave at it, rubbing a violin bow against one edge, etc.), there will be places along that surface that vibrate up and down, and there will also be "nodes" . . . places where the vibrational waves bouncing back-and-forth throughout the plane cancel each other out...

    It takes a few seconds for the waves to propagate through the surface in all directions, before they fall into a "steady state" where some points move up and down a lot, some points move up and down a little, and some stay perfectly still (these are the "nodes").

    . . . only now the nodes are two-dimensional lines instead of points.

    That is what you're seeing in that video. The powder gets bounced around by the parts of the flat surface that are vibrating along with the sine wave, and fall into the "troughs" created by the parts of the flat surface that aren't vibrating at all.

    And that's why it doesn't matter what kind of powder you use... whatever you put there will sit on the "motionless" part of the surface.


    --------------------


    I remember, in a high-level college physics class, when our prof pulled out a piece of flat sheet metal, cut in the shape of a violin. He clamped it at one point, and sprinkled some random powder on top. He then ran a violin bow along the edge of the piece of sheet metal, and the powder fell into these lovely symmetrical line-patterns on the surface.

    That is, in part, why the violin is shaped that way... why something cut into that particular shape sounds so pleasing when it is forced to vibrate.....

    .
    — alanb

    ...........................

    http://alanb.org

    http://www.myspace.com/arsperspicuus

  10. #10
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    Re: OT: A sound physics lesson

    Very fascinating video. It would be interesting to see where else these kaleidoscopic patterns show up.

    I now have a new hobby with my salt shaker and theremin.

    Here's another video with liquid vibrating on a coffee can
    http://youtube.com/watch?v=XlabdhjMn...elated&search=

    Gary Garritan

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