Vibrational eigenmodes of membranes — sand gathers at nodal lines where the membrane stays still.
Shape
Mode (m, n)
Quick presets
(1,1)
(2,1)
(1,2)
(2,2)
(3,2)
(2,3)
(4,3)
(3,4)
Mode (2,3): frequency ∝ √(m²/a² + n²/b²)
Chladni figures were demonstrated with a violin bow on metal plates (E.F.F. Chladni, 1787).
Sand grains migrate to nodal lines — places of zero displacement.