electromagnetic tuning fork, UT2 with variable pitch and resonator
Date: circa 1889
Inventory Number: 1998-1-0274
Classification: Tuning Fork
Dimensions:56 x 68 x 41 cm (22 1/16 x 26 3/4 x 16 1/8 in.)
Bibliography:Catalogue des appareils d'acoustique construits par Rudolph Koenig
DescriptionA heavy cast iron tripod supports an electromagnetic tuning fork and a brass resonator. The fork can be removed so another one of a different frequency, or one not driven by electricity, can be put there. There is a sliding panel on the resonator facing the fork in order to vary the amount of sound going into the resonator. The piston inside the resonator slides from one side to the other manually. The resonator itself is fixed on a pillar, which can be loosened to rotate the resonator out of the way.
The tines of the tuning fork are hollowed out so that mercury could be poured inside them, which was used to vary the sound of the fork. The height of the mercury in the tines was adjusted by a piston found in the steel cylinder at the bottom of the fork. A crank was used to push the piston in and out.
A Lissajous mirror is mounted on one of the tines of the fork.
As several other acoustical instruments in the collection, this one has an old location number inscribed on an oval paper glued to the base: 21-10-1. There are also two old location numbers stamped on this instrument: 21-32 (resonator) and 20-20 (tripod).
Signedon resonator: RUDOLPH KOENIG / À PARIS
Inscribedon tuning fork: UT2 / 256 ± VS / RK
FunctionThe resonator amplifies the sound produced by the tuning fork. The fork is electromagnetically driven. This instrument was used in combination with another electromagnetically driven fork of a fixed pitch, UT2, in order to study beats. The pair had Lissajous mirrors on the forks, which allowed them to be tuned to an exact frequency.
Primary SourcesRudolph Koenig, Catalogue des appareils d'acoustique construits par Rudolph Koenig (Paris, 1889), 66, no. 189.
Related WorksDavid Pantalony, Rudolph Koening (1832-1901), Hermann von Helmholtz (1821-1894) and the Birth of Modern Acoutsics, unpublished dissertation, University of Toronto, 2002.
David Pantalony, "Rudolph Koenig's Workshop of Sound: Instruments, Theories, and the Debate over Combination Tones," Annals of Science 62 (2005): 57-82.
Thomas Greenslade, "The Acoustical Apparatus of Rudolph Koenig," The Physics Teacher, 30 (December, 1992).