The tone variator is a closed-tube sound producing instrument. It consists of a cylindrical brass bottle, the bottom of which is a piston controlled by a delicate cog-wheel mechanism. By means of this the depth of the bottle may be readily changed, thus varying the pitch. The sound is produced by a stream of air directed across the mouth of the bottle through a tube set at the proper angle. A pointer attached to the piston’s setting gear indicates the pitch in terms of vibrations per second.
Proceedings of the Iowa Academy of Science
©1910 Iowa Academy of Science, Inc.
Sylvester, R. H.
"Some Standardizing Tests of Stern's Tone Variator,"
Proceedings of the Iowa Academy of Science, 17(1), 195-197.
Available at: https://scholarworks.uni.edu/pias/vol17/iss1/27