What is cymatics?
Play a steady tone into a metal plate covered in sand and the grains start to run. Within seconds they settle into lines, stars and rings. Change the note and the picture jumps to a new one. That is cymatics: the study of sound made visible.
A name from the 1960s
The word comes from the Greek kyma, meaning wave. It was coined by the Swiss doctor Hans Jenny, who spent the 1960s filming sand, liquids and pastes on vibrating plates and membranes. His book Kymatik (1967) is full of photographs that still look surprisingly modern: hexagons in water, spirals in powder, shapes that seem almost alive.
The patterns themselves were known long before Jenny. In 1680 the English scientist Robert Hooke ran a bow along the edge of a glass plate dusted with flour and saw lines appear. A century later Ernst Chladni turned the trick into a science, and in 1831 Michael Faraday described the ripple patterns that form on a vibrating liquid surface.
Why the sand moves
When a plate vibrates at certain frequencies, it does not simply shake up and down as one piece. It splits into areas that move in opposite directions, like a crowd doing a wave in two halves. Between those areas are thin lines that stay almost still. These are called nodal lines.
Sand on a moving part of the plate gets thrown around. Sand on a nodal line is left alone. After a few seconds, every grain has bounced its way onto a quiet line, and the hidden shape of the vibration becomes visible.
The pattern is a map of where the plate is not moving.
Higher notes, finer patterns
Each plate has its own set of frequencies where these standing patterns appear, called its modes. Low modes give simple shapes: a cross, a circle, two lines. As the frequency rises, the plate splits into more and smaller areas, and the pattern gets busier and more intricate. Between modes, the sand just shivers and blurs.
The shape of the plate matters too. A square plate, a round plate and a violin-shaped plate all give different families of patterns at the same note.
Where it is used today
Cymatics is not only a beautiful demo. Violin and guitar makers sprinkle powder on the wooden plates of an instrument and tap or drive them with a speaker, to check how the wood will ring before the instrument is closed. Engineers use the same idea, with lasers instead of sand, to find vibrations in speakers, car panels and machines. And artists and musicians use it to turn songs into living images.
See it yourself
The Cymatics generator on SeeSound simulates a plate covered in sand. Play a tone, load a track or turn the knob, and watch the grains find their nodal lines in real time. Low notes draw simple figures; push the frequency up and the patterns multiply.