This is a Tonometer.
A tonometer is an instrument that determines the frequency of sounds. It provides carefully measured standards against which other sounds can be compared. First proposed in 1834 by German silk manufacturer Johann Scheibler, the tuning-fork tonometer was brought to mechanical perfection in the late nineteenth century by Parisian acoustic-instrument maker Rudolph Koenig. Employing the technique of optical sound comparison, Koenig used Lissajous figures to refine fork construction. His work almost single-handedly turned the tuning fork into the most precise scientific instrument of the nineteenth century. As a result of this success, Koenig sought to expand into America, and displayed his apparatus at the Philadelphia Centennial Exposition of 1876. He brought samples of his entire stock, including this masterpiece, the Grand Tonomètre, which he demonstrated to leading U.S. scientists. Although surpassed by microphones, oscilloscopes, and other electroacoustic tools in the twentieth century, Koenig’s tonometer represents the height of mechanical acoustic-instrument manufacture of his time.
It is credited
Smithsonian Institution, National Museum of American History, 217544 (600 tuning forks); 248007 (61 tuning forks).
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Its dimensions are
H x W x D: 96.5 x 129.5 x 63.5 cm (38 x 51 x 25 in.)
This object was previously on display as a part of the exhibition Tools: Extending Our Reach.