(or sonorous figures), the figures formed by the accumulation of fine grains of dry sand along the nodal lines on the surface of a vibrating elastic plate or a similar mechanical system. A unique arrangement of the nodal lines corresponds to each of the plate’s normal modes of vibration. The figures were named after their discoverer, E. F. F. Chladni.
The nodal lines may be circular or radial in the case of a circular plate; they are parallel to the edges or the diagonals in the case of rectangular or triangular plates. The various Chladni figures that correspond to the different normal modes of a vibrating plate may be obtained by varying the points where the plate is supported or where it is excited.
Chladni figures are used to study the natural frequencies of the diaphragms of telephones, microphones, and loudspeakers.