What Makes the Resonance Square Experiment a Unique Physics Demonstration?

[Orion1]

I thought that this would be an interesting video for physics majors:
http://www.spikedhumor.com/articles/26352/Resonance_Square.html"

I posted it here, because the experiment appears to involve 'wave function'.
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[Galileo]

Yeah, that's pretty cool. I've never seen such a demonstration live though (but that's okay, because here I can turn down the volume on my speakers).

IIRC the eigenmodes of such a vibration membrane are Bessel functions. The sand will be thrown away from the vibrating places and settle down in the nodal lines, which you can calculate. So by observing the shapes you can directly compare theory and experiment and see which resonance mode you have hit.

 

[Integral]

Here is a site which explains a bit about http://www.phy.davidson.edu/StuHome/jimn/Java/modes.html"

 

[Cyrus]

That was freaking awesome!

 

[Claude Bile]

IIRC the eigenmodes of such a vibration membrane are Bessel functions.

Circular symmetry gives Bessel modes, while cartesian symmetry gives Hermitian modes.

The modes in the demonstration are not Bessel functions or Hermite polynomials, but an interesting blend of both. The blending possibly comes about because you have a membrane with cartesian symmetry, yet the driving force (speaker) is rotationally symmetric.

Claude.