It is a wooden bench (60 x 13 cm) used to study and compare, by means of Chladni's figures, the ways in which three square brass plates (two 20 x 20 cm and 1.5 and 3 mm thick, the third 10 x 10 cm and 1.5 mm thick), fixed at the centres by means of pressure screws and brass rings to three wooden columns (height 18 cm).