A circular metal plate is connected to a frequency generator that causes the plate to vibrate. When sand is sprinkled onto the plate, the sand grains bounce around on the parts of the plate that are moving, but the grains remain still where there are nodes (no movement of the plate).

The circular plate is called a Chladni plate. It will produce a loud sound when a resonant frequency is reached. The sound is much softer for frequencies that do not cause standing waves that fit the plate. The shapes of the standing waves are indicated by the patterns of sand.