Tonoscope

or, the shape of a sound

Every note has a figure. Play one, and a few million grains of light leap off the vibrating surface, then settle along the lines that stay still.

Headphones bring out the low notes.

What you are seeing

A vibrating surface never moves all at once. It divides into regions swinging in opposite directions, separated by lines that stay perfectly still. Sand thrown into the air by the moving regions comes to rest on those still lines and draws them. Ernst Chladni showed this in 1787 by bowing a sand-covered brass plate. In the 1960s Hans Jenny, who coined the word cymatics, sang through a pipe onto a sanded membrane with his tonoscope and watched his voice take shape. The Sing mode here does the same with your microphone.

Here each note excites one standing-wave mode of the chosen resonator, and a few million simulated grains do what the sand did. Higher notes ring in finer modes, so their figures grow more intricate. A chord is the sum of its notes' waves.

The four resonators

Plate: A square plate with free edges, Chladni's own.
Drum: A round membrane held at its rim; its modes are Bessel functions.
Sphere: A ringing shell, vibrating in spherical harmonics.
Lattice: A volume of standing waves whose still places are minimal surfaces: gyroids and their kin.

Color

Each pitch has the color Alexander Scriabin gave it for the light keyboard of his Prometheus (1910). Grains take on the color of whichever note last moved them.

Playing

Click or tap: Plays the note under the pointer, left low to right high. Hold to sustain; drag for a run.
Keyboard: Z to M, A to J and Q to U play three octaves of D Lydian.
Move the pointer: Stirs the grains like a fingertip.
Right-drag, or two fingers: Turns the view. Scroll or pinch to come closer.
1 to 4: Switches the resonator. Space toggles Listen.

Drawn with WebGPU, sounded with the Web Audio API. Set in IM Fell, from type cut in the seventeenth century. Made by cyanheads.