Le Son, Paris, 1869
Around 1800 E. F. F. Chladni discovered the graphic imaging of sound waves (since named after him). His experiments made modes of vibration of surfaces visible for the first time in history. The adjacent chart shows Chladni’s sound images for various vibrations of a metal panel sized 33×33 cm. At first the sheet was covered evenly with fine sand. Borne solely at its centre point, the panel is “played” with a violin bow, in other words set into vibration, and touched simultaneously with two fingers at specific points at the edge. The fine sand is driven away from the antinodes, the places of the strongest vibration, and gathers in the oscillation nodal points: a diagram of (white) nodal lines shows the various modes of vibration of the surface, depending on the touch of the fingers.