Koenig's manometric flame apparatus was a laboratory instrument invented in 1862 by the

German German(s) may refer to: * Germany, the country of the Germans and German things **Germania (Roman era) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizenship in Germany, see also Ge ...

physicist Rudolph Koenig, and used to visualize

sound wave In physics, sound is a vibration that propagates as an acoustic wave through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the ...

s. It was the nearest equivalent of the modern

oscilloscope An oscilloscope (formerly known as an oscillograph, informally scope or O-scope) is a type of electronic test instrument that graphically displays varying voltages of one or more signals as a function of time. Their main purpose is capturing i ...

in the late nineteenth and early twentieth centuries.

Description

The

manometric Pressure measurement is the measurement of an applied force by a fluid (liquid or gas) on a surface. Pressure is typically measured in units of force per unit of surface area. Many techniques have been developed for the measurement of pressur ...

flame apparatus consisted of a chamber which acted in the same way as a modern

microphone A microphone, colloquially called a mic (), or mike, is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and publi ...

. Sound from the source to be measured was concentrated by means of a horn or tube into one half of the capsule chamber. The chamber was divided in two by an elastic diaphragm, usually rubber. The sound caused the diaphragm to vibrate which

modulated Signal modulation is the process of varying one or more properties of a periodic waveform in electronics and telecommunication for the purpose of transmitting information. The process encodes information in form of the modulation or message ...

a flow of flammable illumination gas passing through the other half of the chamber. The illumination gas was passed to a

Bunsen burner A Bunsen burner, named after Robert Bunsen, is a kind of ambient air gas burner used as laboratory equipment; it produces a single open gas flame, and is used for heating, sterilization, and combustion. The gas can be natural gas (which is main ...

, the flame of which would then increase or decrease in size at the same frequency as the sound source.Jim & Rhoda Morris at SciTechAntiques.Flame manometer
Case Western Reserve University Physics Department The change in flame size was too fast to be easily seen with the naked eye, and a

stroboscope A stroboscope, also known as a strobe, is an instrument used to make a cyclically moving object appear to be slow-moving, or stationary. It consists of either a rotating disk with slots or holes or a lamp such as a flashtube which produces br ...

— usually in the form of a rotating many sided mirror — was used to view the flame. The frequency of the sound could then be calculated from the apparent distance between the flame images in the mirror and the known speed of its rotation.

Alexander Graham Bell Alexander Graham Bell (; born Alexander Bell; March 3, 1847 – August 2, 1922) was a Scottish-born Canadian Americans, Canadian-American inventor, scientist, and engineer who is credited with patenting the first practical telephone. He als ...

used this type of equipment to study the performance of his microphones and demonstrated it in his display at the 1876 Philadelphia Centenarian Exhibition. He replaced the rubber diaphragm with an iron disc which was driven by an

electromagnet An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Electromagnets usually consist of wire (likely copper) wound into a electromagnetic coil, coil. A current through the wire creates a magnetic ...

with current fed from a microphone. This apparatus was capable of giving quantitative measures of the performance of his microphones.Manometric Flame Apparatus
Kenyon College A type of Fourier analyzer can be constructed by connecting a number of manometric flame capsules each to a

Helmholtz resonator Helmholtz resonance, also known as wind throb, refers to the phenomenon of air resonance in a cavity, an effect named after the German physicist Hermann von Helmholtz. This type of resonance occurs when air is forced in and out of a cavity (the re ...

tuned to either the

fundamental frequency The fundamental frequency, often referred to simply as the ''fundamental'' (abbreviated as 0 or 1 ), is defined as the lowest frequency of a Periodic signal, periodic waveform. In music, the fundamental is the musical pitch (music), pitch of a n ...

of the sound to be analyzed, or one of its

harmonic In physics, acoustics, and telecommunications, a harmonic is a sinusoidal wave with a frequency that is a positive integer multiple of the ''fundamental frequency'' of a periodic signal. The fundamental frequency is also called the ''1st har ...

s. The flames produced from each capsule are then an indication of the strength of each of the Fourier components of the sound.Fourier Analysis
Kenyon College.

Notes

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References

1

Jim & Rhoda Morris at SciTechAntiques. Accessed March 2008

Kenyon College. Gambier, Ohio. Accessed March 2008

Kenyon College. Gambier, Ohio. Accessed March 2008

Case Western Reserve University Physics Department. Accessed March 2008 Measuring instruments Laboratory equipment History of physics