Savart’s Wheel, designed by Bart Hopkin, is widely acclaimed for the fact that it makes the most obtrusive, obnoxious and irritating sound ever known. The instrument is made up of a series of disks of graduated size mounted on a motorized spindle. The exposed outer edge of each disk is lined with ridged material, with ridges spaced about 1/8 inch apart.
“Baby Please Don’t Go,” played on Savart’s Wheel
With the spindle rotating, the player holds a sort of plectrum against the ridges as they rotate past, resulting in some number of ridge-bumps against the plectrum per second. That frequency is the frequency you hear; it is what provides the pitch. For each differently sized disk, the ridges agitate the plectrum at a different frequency (the larger the disk, the more ridges go by per second), and so the instrument is capable of playing clear melodies.
The plectrum piece is attached to a styrofoam cup. This provides a larger, lightweight surface which acts as a soundboard, projecting the vibration that the plectrum experiences out into the air. In the photo, the plectrum/soundboard pieces (there are two of them) are seen lying in front of the main instrument.
This is one of the instruments featured in the CD Instrumentarium Hopkinis: Bart Hopkin Plays Invented Instruments. You can hear a short excerpt featuring Savart’s Wheel by activating the sound controller above.
A more complete description of Savart’s Wheel appeared in the Experimental Musical Instruments quarterly journal, Volume 11 #1, September 1995. This and all of ExMI’s back issues remain available.