sound wave interference demonstration apparatus
Date: circa 1889
Inventory Number: 1997-1-0902a,b
Classification: Acoustic Instrument
Subject:
Maker: Rudolph Koenig (1832 - 1901)
Maker: Department of Physics, Harvard University ? (founded 1884)
Cultural Region:
Place of Origin:
City of Use:
Dimensions:
part a: 17.9 × 12.6 × 9.4 cm (7 1/16 × 4 15/16 × 3 11/16 in.)
part b (largest piece): 26.4 × 107.4 × 5.9 cm (10 3/8 × 42 5/16 × 2 5/16 in.)
box: 15.2 × 109.9 × 26 cm (6 × 43 1/4 × 10 1/4 in.)
Accessories: six pieces of metal piping (in small archival ziploc bag); two detachable wooden legs for the body of the instrument; block of two manometric capsules
Description:
Part (a) is a symmetrical arrangement of brass pipes, shaped like a trombone, mounted on a horizontal maple stand. The pipes on the right side of the instrument can be extended outward to adjust the distance that sound from a tuning fork or other noise making device must travel. A boxwood scale (0-34cm) allows for the determination of the wavelength of simple tones.
Part (b) is a block of two manometric capsules, fitted with two tubes that slide onto the center holes of part (a).
Part (b) is a block of two manometric capsules, fitted with two tubes that slide onto the center holes of part (a).
SignedRUDOLPH KOENIG À PARIS
FunctionThis device was used to demonstrate what happens when two sound waves interact with each other. The principle is that one places a sound source at one point in the pipe system, and the resulting waves travel along two different paths before meeting again at an exit point. Depending on the difference in distance between the two paths (which can be changed, and is registered on a scale), one will hear constructive or destructive interference. The wavelength of the sound is also clearly visualized as the distance between consecutive settings for maximum constructive or destructive interference.
Several of the pipe fittings indicate its use with a flammable gas, which was also used to visualize directly the sound vibrations, as the flickering of a flame fed from the pipes carrying the sound. These could be further analyzed with the use of a rotating mirror as described in more detail below.
According to Koenig's 1889 catalog (87-88, no. 243), this device would be used with a tuning fork stand (no. 38 in the catalog, p. 21), and a resonator (catalog p. 25, no. 54; objects 2000-1-0010a-e). In that setup, the two branches of the forking tube would be connected with the open tubes on one side of the instrument. One end of a resonator would be placed in that tube. Then a tuning fork, preferably on a stand, would be placed behind the resonator.
On the other side would be the manometric flame apparatus. Historian David Pantalony describes the apparatus in his book Altered Sensations: "A thin membrane divided the capsule into two parts: one part was open to the sound vibrations under study; the other was closed to a flow of gas that came in through an input and exited through a gas jet, which was lit creating a tiny candle-sized flame. The membrane picked up vibrations in the air and transferred these vibrations to the gas, which caused the flame to flicker. A rotating mirror spreads the flickering flame across the surface of the mirror through persistence of vision. The pattern of flame flickerings resemble a saw-tooth pattern of ups and down that would otherwise be imperceptible to the viewer" (317). Pantalony, in his article "Rudolph Koenig's Workshop of Sound," has compared the manometric flame to a "mechanical oscilloscope" (64).
According to John Tyndall in his book Sound, the device can be used to measure the interference of waves: "Drawing [the tube] out, a point is at length obtained where the sound of the fork is extinguished. This occurs when the distance ab [the amount the tube is drawn out] is one fourth of a wavelength; or, in other words, when the whole right-hand branch is half a wavelength longer than the left hand one" (365).
Several of the pipe fittings indicate its use with a flammable gas, which was also used to visualize directly the sound vibrations, as the flickering of a flame fed from the pipes carrying the sound. These could be further analyzed with the use of a rotating mirror as described in more detail below.
According to Koenig's 1889 catalog (87-88, no. 243), this device would be used with a tuning fork stand (no. 38 in the catalog, p. 21), and a resonator (catalog p. 25, no. 54; objects 2000-1-0010a-e). In that setup, the two branches of the forking tube would be connected with the open tubes on one side of the instrument. One end of a resonator would be placed in that tube. Then a tuning fork, preferably on a stand, would be placed behind the resonator.
On the other side would be the manometric flame apparatus. Historian David Pantalony describes the apparatus in his book Altered Sensations: "A thin membrane divided the capsule into two parts: one part was open to the sound vibrations under study; the other was closed to a flow of gas that came in through an input and exited through a gas jet, which was lit creating a tiny candle-sized flame. The membrane picked up vibrations in the air and transferred these vibrations to the gas, which caused the flame to flicker. A rotating mirror spreads the flickering flame across the surface of the mirror through persistence of vision. The pattern of flame flickerings resemble a saw-tooth pattern of ups and down that would otherwise be imperceptible to the viewer" (317). Pantalony, in his article "Rudolph Koenig's Workshop of Sound," has compared the manometric flame to a "mechanical oscilloscope" (64).
According to John Tyndall in his book Sound, the device can be used to measure the interference of waves: "Drawing [the tube] out, a point is at length obtained where the sound of the fork is extinguished. This occurs when the distance ab [the amount the tube is drawn out] is one fourth of a wavelength; or, in other words, when the whole right-hand branch is half a wavelength longer than the left hand one" (365).
Historical AttributesTags with such numbers are found on instruments are found on acoustic instruments used in the Physics Department, Harvard University.
Curatorial Remarkson tag attached to instrument (not recently found with instrument): EXPER ON SOUND INTERFERENCE. TYNDALL SOUND (1867), pg. 261 22-3-6, 21-2
Pipes 1997-1-1034 and 1997-1-1036 may be related to or meant to be used with this instrument.
1997-1-0902a and b are housed together in the same blue-board box with no lid.
Pipes 1997-1-1034 and 1997-1-1036 may be related to or meant to be used with this instrument.
1997-1-0902a and b are housed together in the same blue-board box with no lid.
Primary SourcesFor an illustration of a modified version of this instrument (the tubes are upright) and a description, see Rudolph Koenig, Catalogue des appareils d'acoustique construits par Rudolph Koenig (Paris, 1889), pp. 87-88, no. 243.
ProvenanceSee Historical Attributions.
