P.C. wrote:
[div style="font-style: italic;"]I suppose it's only logical that sound waves would have a pattern....but to SEE it is awsome. It's almost like having a glimpse of what it might be like to have synesthesia.[/div]
This is actually a very common phenomenon in physics and it occurs in various ways across the entire energy spectrum. Everything vibrates or 'rings' when pulsed with energy. Their demonstration is a cool way to see the stable harmonics produced in the plate by the vibrations.
For example, if the vibrate the plate at 2000 hz (cycles per second) the plate will 'ring' or self-oscillate at other frequencies as well which are always multiples of the original frequency. So it may oscillate (ring) at 4000 hz, 6000 hz, 8000 hz, and so on. The waves can combine in either an additive way or a subtractive way, reinforcing the wave amplitude or canceling it out. You'll see this in [a href="http://mathworld.wolfram.com/LissajousCurve.html"]Lissajous patterns[/a] in oscilliscopes and all sorts of other places- wherever energy gets expresssed, basically.
The plate (or other object) may also happen to ring at other frequencies as well, and that's where it can get interesting. These frequencies usually cause lots of oddball distortions of the patterns being generated, and when you cycle one of the frequencies up and down it causes all sorts of other transient patterns to appear and disappear.
Check out the [font style="font-weight: bold;" size="2"][a href="http://www.math.com/students/wonders/lissajous/lissajous.html"]Lissajous Lab[/a][/font]
