Physics
Normal Modes
Every object has a few shapes it can hold while it vibrates, each ringing at its own note. Pluck it and the motion splits into those notes: whole multiples on a string, an untuned jumble on a drum.
above restbelow restnodessand
Drag the string to pull it and let go to pluck. In the spectrum, drag a bar up or down to mix that mode in; click a bar to play it alone.
Mode n = 1: f / f₁—
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Object
slowfast
Numbers
Modes playing—
Selected mode—
Its amplitude—
Its nodes—
Whole shape repeats—
What to observe
- Mix a few string modes. Each runs exactly n times as fast as the fundamental, so every bar sits on a whole number and the whole shape repeats once per fundamental period.
- Pluck the string at its middle and every even bar stays at zero: each even mode has a node there, so the pluck cannot reach it.
- A single drum mode stands still, and the sand is shaken off wherever the skin moves and piles up on the nodal lines. Two modes with the same note, (1,3) and (3,1), draw a figure of their own.
- Poke the round drum: its overtones land at 1.59, 2.14, 2.30 times the fundamental, between the whole-number lines. Turn on Sound and compare it with the string.
Shortcuts:space run/pause · r reset · f fullscreen