Acoustic apparatus · after Ernst Chladni, 1787

The Chladni Plate

Sand on a steel plate. Drive it at the wrong frequency and nothing happens. Hit a resonance and the grains flee the shaking regions and pile up along the lines that stand perfectly still. There are 21 figures hidden in this dial. Go find them.

Plate I · square steel · 312 Hz
Resonance

What you're looking at

Each grain takes a random hop every frame, and hops harder where the plate moves more. So it random-walks until it stumbles onto a nodal line— a place with no motion — and then it stops. The pattern isn't drawn. It's what's left over.

Finding a figure

Drag the dial coarsely, then hold the arrow keys to creep 1 Hz at a time. The meter under the dial is the plate's response. Above about 80% the figure snaps into focus and gets logged. Sweep hunts for you, slowing as it nears one.

The modes

A square plate rings at frequencies set by two whole numbers — how many half-waves fit across it each way. Higher pairs sit closer together, so the top of the dial is crowded and the figures there are hard to isolate. That is also true of real plates.

What you're hearing

Turn on Sound and the dial becomes a pitch. Loudness tracks the plate's real response, so between resonances you hear the bow and little else, and the tone blooms as a figure forms. Each figure carries its own interval, taken from its two mode numbers: 2,1 is an octave, 3,2 a fifth, 4,3 a fourth. The crowded high modes are the dissonant ones. Run Sweep with the sound up.

How this got built

I asked Claude Opus for “something fun” and gave it nothing else. No spec, no audience, no constraint. It came back with an acoustics experiment from 1787, then built the colour palette out of brass instruments and picked a condensed typeface because a plate is an instrument panel. None of that was in the prompt.

It also shipped a bug worth keeping. The first confidence meter scored the winning mode as a share of all modes, so at 150 Hz it read 99.99% certain on a plate that wasn't moving at all. A ratio doesn't care about scale. When I later asked for sound, it derived the musical intervals from the same two whole numbers that decide each figure's shape.

Read the full build log →