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  1. Standard member Hand of Hecate
    Merciless Vagabond
    13 Mar '13 03:08
    http://www.youtube.com/watch?feature=player_embedded&v=uENITui5_jU
  2. Standard member Grampy Bobby
    Boston Lad
    13 Mar '13 06:45
    Originally posted by Hand of Hecate
    http://www.youtube.com/watch?feature=player_embedded&v=uENITui5_jU
    Amazing, I want one for Christmas.
  3. 13 Mar '13 09:42
    Originally posted by Hand of Hecate
    http://www.youtube.com/watch?feature=player_embedded&v=uENITui5_jU
    I assume this effect cannot be seen directly with the unaided eye and can only be seen with a camera with its fps tuned in to the frequency of the sound?
  4. Standard member Kepler
    Demon Duck
    13 Mar '13 09:48
    Originally posted by humy
    I assume this effect cannot be seen directly with the unaided eye and can only be seen with a camera with its fps tuned in to the frequency of the sound?
    It looks as if the camera has not been fiddled with at all. The hand turning the control for the sound does so in real time and the effect appears. I would think it is some kind of standing wave phenomenon.
  5. 13 Mar '13 10:59 / 1 edit
    Originally posted by Kepler
    It looks as if the camera has not been fiddled with at all. The hand turning the control for the sound does so in real time and the effect appears. I would think it is some kind of standing wave phenomenon.
    It looks as if the camera has not been fiddled with at all.

    but it does say just after the start of the video in big yellow writing


    ....
    - tone generating software
    - producing a 24hz sine wavelength
    - 24 fps capable camera

    so I assume this implies that the 24 fps is needed for the 24hz sine wave to actually see the effect?
  6. Standard member sonhouse
    Fast and Curious
    13 Mar '13 11:17 / 1 edit
    Originally posted by humy
    It looks as if the camera has not been fiddled with at all.

    but it does say just after the start of the video in big yellow writing


    ....
    - tone generating software
    - producing a 24hz sine wavelength
    - 24 fps capable camera

    so I assume this implies that the 24 fps is needed for the 24hz sine wave to actually see the effect?
    You can see the hose vibrating back and forth in time with the speaker so at 20+ Hz, which means the camera was doing a slo mo. You would not see what you see in the video. It would be going faster than you could make it out.

    I just had a brain fart, I think you could see the effect directly if you used a variable speed stroboscope. We just bought one, they are a lot more advanced now than the old xenon tube models of the past. Now it is a box the size of a pack of cigarettes with
    LED's instead of Xenon tubes, now powered by a couple of AA cells and the LED one I have has two brightness settings, one too bright to use indoors! It can be set anywhere from one pulse per second to over 10,000.

    I bet it would freeze the water image so you can see the effect directly.
  7. 13 Mar '13 12:39 / 3 edits
    Originally posted by sonhouse
    You can see the hose vibrating back and forth in time with the speaker so at 20+ Hz, which means the camera was doing a slo mo. You would not see what you see in the video. It would be going faster than you could make it out.

    I just had a brain fart, I think you could see the effect directly if you used a variable speed stroboscope. We just bought one, t d to over 10,000.

    I bet it would freeze the water image so you can see the effect directly.
    Interesting.

    I just had a brain fart,
    your brain can fart?
  8. Standard member sonhouse
    Fast and Curious
    13 Mar '13 16:06 / 1 edit
    Originally posted by humy
    Interesting.

    I just had a brain fart,
    your brain can fart?
    You would be surprised what my brain can do If you ignited it, farts being methane, it would convert into a brain flash
  9. Standard member wolfgang59
    Infidel
    13 Mar '13 18:57 / 1 edit
    Originally posted by Hand of Hecate
    http://www.youtube.com/watch?feature=player_embedded&v=uENITui5_jU
    Brilliant ... I would not have expected that!

    This would be a brilliant science lesson on sound waves, I particularly
    liked the "backward" effect.

    Did tou see the comments?
    That's a glitch. God will fix that in the next release CLASSIC
  10. 13 Mar '13 21:25
    Originally posted by Hand of Hecate
    http://www.youtube.com/watch?feature=player_embedded&v=uENITui5_jU
    Outstanding!.
  11. Standard member Hand of Hecate
    Merciless Vagabond
    13 Mar '13 22:33
    Originally posted by humy
    It looks as if the camera has not been fiddled with at all.

    but it does say just after the start of the video in big yellow writing


    ....
    - tone generating software
    - producing a 24hz sine wavelength
    - 24 fps capable camera

    so I assume this implies that the 24 fps is needed for the 24hz sine wave to actually see the effect?
    I believe you are right. Without the camera frame rate at 24 for I don't think you'd see the water as a fixed wave form, rather it would be appear to be moving.
  12. 14 Mar '13 22:42 / 2 edits
    Originally posted by Hand of Hecate
    I believe you are right. Without the camera frame rate at 24 for I don't think you'd see the water as a fixed wave form, rather it would be appear to be moving.
    Yes. The effect is called aliasing. It is the same reason helicopter rotors sometimes appear stationary in a video when they're actually rotating.

    In this video, the pipe itself is vibrating and in every frame you see it in exactly the same position. Thus, because the entire thing is periodic, the water stream has a shape that is repeated in time with the same frequency and that one particular shape is what you're seeing.

    P.S. That's also why when he increases the frequency to 25 Hz, it looks like slow motion. This would be a great thing to show in any DSP class as an example.