Singing plates. A metal plate is bowed at one frequency. Wherever it vibrates, the sand is thrown off; it comes to rest only on the nodal lines, the parts of the plate that stand still. Every resonance draws its own figure, as Ernst Chladni showed in 1787. Here the plate drifts from one resonance to the next, and the coloured sand is dragged along, marbling as the figures change. Drag the bar to tune · touch the plate to hold a node · click to tap the sand.
Singing plates
Sound made visible: sand dancing on a vibrating plate.
How it works
Nodal lines. When a metal plate vibrates at one of its resonant frequencies, some lines on it stay perfectly still. Sand is shaken off everywhere else and gathers on those lines, drawing the shape of the vibration.
Ernst Chladni, 1787. Chladni drew a violin bow along the edge of sand-covered plates and published the figures in 1787. Napoleon was so impressed that he offered a prize for their mathematical explanation, which Sophie Germain won in 1816.
Here. The plate drifts slowly from one resonance to the next, and the coloured sand is carried along to each new figure. Drag the bar to tune it yourself, touch the plate to hold a still point, or click to tap the sand.