These instruments demonstrate the “communication of vibrations” between connected plates. This was a topic first investigated by the French scientist Felix Savart, in the 1820s. Savart experimented with a pair of identical glass disks that were connected by only a single glass rod. When the two disks were sprinkled with sand and the first one vibrated, both disks formed identical patterns.
Source: Steven Turner; Curator, Physical Sciences, National Museum of American History, Smithsonian Institution.
This rack has 3 square and 3 circular brass plates of varying dimensions. It was used to demonstrate the effect of changes in the size and thickness of plates on both their tone and the Chladni figures that they produce. A plate that is the same size as the one next to it, but double the thickness, will produce a note twice as high, while a plate that is half the area of the one next to it, but double the thickness, will sound a note that is four times higher.
Armstrong Cork,. 1932. “Armstrong's Acoustical Products”. Corkoustic, Ceramacoustic For Acoustical Correction Of Churches, Auditoriums, And Theatres, And Noise-Quieting Of Banks, Schools, Hospitals, Offices, Sunday School Rooms, Factories, And Other Public Buildings. Lancaster, PA.
„This instrument was used in an Ohio high school and probably dates from the late 19th or early 20th centuries. The replication of classic experiments was a common way to teach science at this time, and Chladni’s figures were considered to be both instructive and beautiful.
The German scientist Ernst Chladni was one of the pioneers of experimental acoustics. His research on different kinds of vibrations served as the basis for the scientific understanding of sound that later emerged in the 19th century.
André Prosper Crova was a faculty member at the University of Montpelier. He invented this acoustic wave model in the 1860s and commissioned the prominent Parisian acoustic instrument maker Rudolph Koenig to manufacture it for him. It was first shown at the 1867 Paris World Fair.