Accession No


Brief Description

set of Helmholtz resonators, probably originally used in King’s College, London, as part of an apparatus for the visual analysis of sound, by Rudolph Koenig, late 19th Century



Koenig, Rudolph [resonators] unknown [frame]



Earliest Date

Jan. 1, 1860

Latest Date

Dec. 31, 1900

Inscription Date


metal (brass); wood


height 840mm; breadth 475mm; depth 342mm

Special Collection


Purchased from King’s College, London, England, 10/1986. Purchased with the assistance of a grant from PRISM Fund.


[All of the brass resonators carry Koenig’s maker’s mark:] RK

Description Notes

Set of Helmholtz resonators, by Rudolph Koenig, late 19th century, probably originally used in King’s College, London, as part of an apparatus for the visual analysis of sound.

10 brass Helmholtz resonators set in vertical tapering wooden stand, and held in place by wooden rings, with the largest resonator at the bottom. Wooden rings secured to stand by wooden pillars and brass bolts. Related paper label: ‘Helmholtz’s resonator’.

Note: Only the brass resonators themselves carry Koenig’s makers mark - it is not clear whether the stand was included with the original set, as sold by Koenig, or not. The stand may, for example, have been made by a technician at King’s College.

Condition good; complete


Torben Rees; 'Koenig's apparatus for the analysis of sound: the first spectrum analyzer'; Explore Whipple Collections online article; Whipple Museum of the History of Science; University of Cambridge; 2009:


This object consists of ten Helmholtz resonators arranged in a wooden frame, and was acquired from King’s College, London, in the 1980s. Rudolph Koenig, a Parisian physicist and acoustical instrument maker, made the resonators in the late 19th century, but the maker of the frame is not certain. Most probably this apparatus was assembled at King’s College as part of a version of Koenig’s apparatus for the analysis of sound, using a standard set of resonators.

Musical sounds and the vowel sounds of human speech have their particular sound quality, or timbre, in virtue of the specific combinations of upper partial frequencies at various intensities. That is, a musical note at concert A 440Hz will contain that fundamental frequency as well as a series of harmonic partials at multiples of this fundamental (880Hz, 1320Hz, etc.) at various intensities. Using resonators held against his ear, Herman Helmholtz was able to detect the presence of these upper partials and thus perform an analysis of the sound (for more on how such resonators work, see the catalogue entries for Wh. 4612). This practice, however, left an unwelcome element of subjectivity in acoustic experimentation. Koenig removed this subjectivity by designing a way to visualize the specific composition of sounds.

In Koenig’s design (see photograph) each resonator has one end open to the air and the other end attached to a rubber pipe. That pipe is connected to a manometric capsule, consisting of two hemispheres separated by a thin rubber diaphragm. One hemisphere is connected to the resonator via the pipe, and through the other hemisphere flows a flammable gas, which burns at the end of a narrow jet pipe at the top. The pressure of the gas in the capsule is dependent on the pressure of the air in the other hemisphere, which in turn is dependent on the vibrations of air within the resonator. Thus, during resonance, the gas flame vibrates in sympathy rendering visible the presence of the given frequency in the sound under investigation. An experimenter would then sing or make a sound in front of the open resonators and observe the vibrations of the flame in a rotating mirror, acting like a stroboscope, which made to easier to see the vibrations.

Flame manometers were also used with the “Trombone de Koenig” (see catalogue entry for Wh. 6217) as well as for many other acoustical experiments.
Created by: Dr. Torben Rees on 05/06/2008


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