This is a set of 16 Helmholtz resonators. Made from sections of brass that were spun on a lathe, they are wonderfully light and easy to hold. Helmholtz designed them to demonstrate his theory that all vowel and musical sounds are composed of combinations of simple, pure notes (Helmholtz’s “Theory of Timbre”). He correctly observed that musical sounds, particularly the higher tones, are often perceived as a single mass of sound.

„In 1862, the German scientist Herman Helmholtz invented another important acoustic instrument, the double siren. The new instrument combined two Dove Sirens, which were positioned to face each other and coupled on the same shaft. Both sirens were also connected to the same air supply, which made it possible to produce a variety of frequencies, all of which would slide up or down the scale as the air pressure was increased or decreased.

„The acoustic siren was one of the fundamental tools of 19th century science. Invented by the French scientist Cagniard de la Tour, in 1819, the siren used a bellows apparatus to force air through two brass disks. As the air passed through holes in the discs, one of which was rotating, it produced a series of regular pressure waves that we perceive as a musical tone. The construction of the siren allowed that tone to be raised or lowered by simply increasing or decreasing the speed of the rotating disc. 

This set of 3 tuning forks, each mounted on its’ own resonator box, was made in Paris between about 1870 and 1900. The tuning forks were each milled from a single blank of fine steel and were then precisely tuned to produce a single, specific, tone. The resonator boxes that they are bolted to are wood, made from the same spruce often used in stringed musical instruments. Spruce wood is naturally responsive to sound vibrations and is the ideal material for this application.

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.

This apparatus consists of three wires, each bent to resemble transverse waves. The wires are mounted in a rectangular brass box that was placed in front of the lens of a projector. The top two wires are identical, but positioned so that their shadows appear to move in opposite directions as a crank on the side of the box is turned. As they do this, the crests and troughs of the waves alternately lineup and overlap. The corresponding “interference” of the two waves is seen in the changing shape of the third wire.