Cymatics is the study of visible sound and vibration. The phenomenon is visualized through various materials: powder on rigid surfaces, fluids, liquid paste and also digital imaging techniques. I’m most fascinated by the very simple analog experiments.
Ernst Chladni used a violin bow along the edge of a metal plate to reveal the so-called Chladni patterns. Today of course we use more sophisticated tone generators, the rest stays the same. In the last century, Hans Jenny coined the term Cymatics. He was the kind of Renaissance man: physician, fine artist, pianist, philosopher, historian, and empirical researcher. The second and third video attached is by him.
Today there are a lot of people carrying on the torch with great experiments. For example Alexander Lauterwasser (most of the pictures after the videos are from his lab).
Chladni patterns at increasing frequencies
Hans Jenny: Cymatics — Bringing Matter to Life With Sound
The following shots are from here: