# Chladni Plate

A black plate on a shaker, strewn with sand, with a frequency knob. Turn it onto a resonance and the plate sings: the sand walks off the parts that move and gathers on the lines that stand still. Bow it along an edge, lay a finger on it, tap it: it answers where you touch it.

Object · With a Pass · https://tactileui.dev/objects/chladni

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## Anatomy

Plate modes, Drive point, Bowed edge, Finger damping, Damped resonance, Plate energy ring down, Sand on nodal lines, Tap arcs, Grain density imagedata, Log scale knob, Lock lamp, Css shimmer, Sleeping loop

## Usage notes

A control that answers with a picture: tuning an audio product, a hero that rewards playing it, a loading state that settles into a figure, a signature drawn from a pair of numbers. The knob is a real slider in hertz on a log scale, spoken with the bow, the finger and the figure it rings in; each resonance is a detent and a lock lamp goes amber, then green; arrows fine-tune, Page keys jump to the next resonance. Bow the plate along an edge and it plays where the bow touches, and rings on after; hold a finger on it and the modes that move there give way; tap it and the sand jumps. Drive is a toggle, Damp a toggle, Bow and Strew keys, B bows.

## Options

| Option | Type | Description |
| - | - | - |
| frequency | number | The plate rings at each of its modes and the sand draws that mode’s figure; between them it shivers, more the nearer a mode. Page keys on the knob jump to the next resonance the drive can find. |
| drive | boolean | The shaker drives the plate at its centre, which moves only some of its modes. Off, the plate rings down and the sand stays where it lies; a bow along an edge still plays it. |
| grains | number | Grains of sand |
| finish | enum | Auto follows the page: the case, knob, keys and display are drawn from the page’s finish (a printed case on Paper, a lit display on Phosphor); without the kit’s tokens, aluminium on a light page and graphite on a dark one. On a light finish the plate is that finish’s own light metal, porcelain or stock and the sand dark; on a dark one it is anodised with pale sand, lit on Phosphor and Night. Pinned finishes keep the black plate. |
| light | number | The plate’s bevel and the driver cap catch it; the grains’ shadows fall away from it. |
| sound | boolean | Plays the drive and a quieter octave, its loudness following the plate’s energy: it swells as a bow is drawn and dies as the plate rings down. Off by default; never under reduced motion. |
| readonly | boolean | Read-only |
| label | text | Accessible name |

## Methods

- frequency
- mode
- energy
- bowed
- update
- setFrequency
- strew
- bow
- stopBow
- damp
- tap
- setPour
- glide
- stopGlide
- destroy

## States

1. **Strewn**: Sand evenly over the black plate; the display gives the frequency.
2. **On a resonance**: The display names the mode and its lamp is green; the sand hops off the moving parts and drifts onto the nodal lines, and the figure draws itself in a second or two.
3. **Nearing one**: The lamp is amber; the plate rings, and the sand shivers, more the nearer the knob is to a mode. Landing on it snaps the sand into the figure.
4. **Bowed**: A press at an edge drawn along it is a bow: a stick and horsehair lie beside the edge and a lit mark shows where it touches. Where it touches picks the mode that answers; how fast it goes sets how hard the plate rings.
5. **Ringing down**: The bow lifts, or the drive is switched off.
6. **Fingered**: A finger held on the plate damps what moves under it, and a soft shadow shows where. The figure reorganises round it; moving the finger changes which figure wins.
7. **Tapped**: A short press throws the sand near it outward on small arcs, brighter and larger while airborne, and it falls back under whatever energy is left.
8. **Pouring**: Alt-drag, or a Pour stroke, drops a pinch of sand; on a resonance it runs to the lines.
9. **Singing**: While the plate rings a faint shimmer follows the figure: the parts moving up and those moving down alternate. A CSS animation; it stops as the plate rings down.
10. **Drive off**: The lamp on the Drive key goes out; the plate rings down and the sand stays where it lies. A bow still plays it.
11. **Tone**: Optional: a sine at the drive and a quieter octave, following the plate's energy. Off by default.
12. **Aluminium**: A bead-blasted case, a turned knob, a reflective LCD.
13. **Graphite**: A soft-touch case, a dark knob, a vacuum-fluorescent display.
14. **Read-only**: A display of a figure: the knob, keys and plate do nothing.
15. **Off screen or hidden**: Paused, and the tone and the shimmer stop.
16. **Reduced motion**: The figure appears at once, also for a bow or a finger; no arcs, no ring-down, no shimmer, no tone.

## How it works

Original. The plate itself is baked once per size.