Named after Ernst Chladni, this experiment consists of a rigid metal plate covered in sand or similar material, that gets vibrated at various frequencies and produces interesting patterns. The sand initially bounces about on the plate until it settles in the areas of zero movement (nodal points).

The example in this video has been set to music which is more pleasing for most people, but if you want to hear it with the original tones go to this YouTube page instead. Lower your volume first!