Vibrations of plates, Chladni's figures

This video demonstrates the principle of Chladni figures and vibrating plates.

Brass plates of different shapes are fixed centrally at the top of wooden columns. Sand is spread on a circular plate. The plate vibrates and emits a sound when its rim is rubbed by a bow. The nodal lines of the vibration mode are displayed by the figures formed by the sand that accumulates along them (Chladni figures). The same experiment is repeated with a circular plate of smaller diameter. The different figures obtained with a square plate depend on where and how it is rubbed by the collector. The vibrations of the plate can also excite the oscillation of a thin paper membrane.