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at resonance is not exactly equal to a multiple of the half-wavelength. Because the air at the source end of the tube, next to the speaker's diaphragm, is vibrating, it is not exactly at a node (point of zero amplitude) of the standing wave. The node actually occurs some distance beyond the end of the tube. Kundt's method allowed the actual locations of the nodes to be determined with great accuracy.
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25:
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A less accurate method of determining wavelength with a tube, used before Kundt, is simply to measure the length of the tube at resonance, which is approximately equal to a multiple of a half wavelength. The problem with this method is that when a tube of air is driven by a sound source, its length
262:
By filling the tube with other gases besides air, and partially evacuating it with a vacuum pump, Kundt was also able to calculate the speed of sound in different gases at different pressures. To create his vibrations, Kundt stopped the other end of the tube with a loose-fitting stopper attached to
289:
398:{\displaystyle {\frac {c_{\text{metal}}}{c_{\text{air}}}}={\frac {f\lambda _{\text{metal}}}{f\lambda _{\text{air}}}}={\frac {\lambda _{\text{metal}}}{\lambda _{\text{air}}}}={\frac {L}{d}}\,}
111:
rod. The experiment is still taught today due to its ability to demonstrate longitudinal waves in a gas (which can often be difficult to visualise). It is used today only for demonstrating
189:. The powder is caught up in the moving air and settles in little piles or lines at these nodes, because the air is still and quiet there. The distance between the piles is one half
275:, giving out a high note. Once the speed of sound in the air was known, this allowed Kundt to calculate the speed of sound in the metal of the resonator rod. The length of the rod
417:
A modern version of Kundt's tube experiment, used in a South
American university physics class. Instead of a transparent tube with powder in it to reveal the nodes, this uses
239:
162:
The sound generator is turned on and the piston is adjusted until the sound from the tube suddenly gets much louder. This indicates that the tube is at
46:
33:
479:"Ueber eine neue Art Akustischer Staubfiguren und über die Anwendung derselben zur Bestimmung der Shallgeschwindigkeit in festen Körpern und Gasen"
911:
283:
was equal to a half wavelength of the sound in air. So the ratio of the two was equal to the ratio of the speed of sound in the two materials:
166:. This means the length of the round-trip path of the sound waves, from one end of the tube to the other and back again, is a multiple of the
263:
the end of a metal rod projecting into the tube, clamped at its center. When it was rubbed lengthwise with a piece of leather coated with
177:. Therefore, the length of the tube is a multiple of half a wavelength. At this point, the sound waves in the tube are in the form of
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159:. The other end of the tube is blocked by a movable piston which can be used to adjust the length of the tube.
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of the wave the sound pressure goes to zero. The sound power from the microphones is recorded on the
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was equal to a half wavelength of the sound in metal, and the distance between the piles of powder
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that he caused to vibrate or 'ring' by rubbing it, but modern demonstrations usually use a
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Hortvet, J. (1902). A manual of elementary practical physics. Minneapolis: H.W. Wilson.
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of vibrations of air is zero at equally spaced intervals along the tube, called the
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of the sound is known, multiplying it by the wavelength gives the speed of sound
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708:
459:, demonstrates the relationship between standing sound waves and sound pressure.
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148:
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The London, Edinburgh, and Dublin
Philosophical Magazine and Journal of Science
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196:/2 of the sound. By measuring the distance between the piles, the wavelength
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horizontal pipe which contains a small amount of a fine powder such as
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139:. At one end of the tube is a source of sound at a single frequency (a
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The detailed motion of the powder is actually due to an effect called
530:. Vol. 35, no. 4. UK: Taylor & Francis. pp. 41–48
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is moved back and forth. When the microphone's position is at the
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561:(3rd ed.). London: Charles Griffin & Co. pp.
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caused by the interaction of the sound wave with the
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of the sound in air can be found. If the frequency
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864:
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453:, another standing wave visualization technique.
585:. UK: Cambridge University Press. p. 287.
95:apparatus invented in 1866 by German physicist
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8:
70:Drawing from Kundt's original 1866 paper in
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489:(4). Leipzig: J. C. Poggendorff: 497–523.
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49:of all important aspects of the article.
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80:and the powder patterns created by it
45:Please consider expanding the lead to
76:, showing the Kundt's tube apparatus
7:
522:Kundt, August (January–June 1868).
254:of air at the surface of the tube.
14:
421:mounted in the tube. The piston
16:Experimental acoustical apparatus
988:
987:
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23:
37:may be too short to adequately
47:provide an accessible overview
1:
582:Fluid Dynamics for Physicists
234:{\displaystyle c=\lambda f\,}
558:A Textbook of Physics: Sound
143:). Kundt used a metal rod
99:for the measurement of the
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983:
695:
503:10.1002/andp.18662030402
664:Architectural acoustics
567:Kundt's tube resonance.
115:and acoustical forces.
751:Fletcher–Munson curves
746:Equal-loudness contour
656:Acoustical engineering
551:Poynting, John Henry;
524:"Acoustic Experiments"
437:
399:
235:
85:
887:Hermann von Helmholtz
785:Fundamental frequency
689:Sympathetic resonance
579:Faber, T. E. (1995).
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273:fundamental frequency
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290:
215:
78:(fig.6 & 7, top)
907:Werner Meyer-Eppler
817:Missing fundamental
495:1866AnP...203..497K
409:Reason for accuracy
267:, the rod vibrated
258:Further experiments
91:is an experimental
790:Frequency spectrum
483:Annalen der Physik
477:Kundt, A. (1866).
438:
395:
247:acoustic streaming
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86:
73:Annalen der Physik
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963:Musical acoustics
795:harmonic spectrum
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892:Carleen Hutchins
824:Combination tone
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684:String vibration
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153:signal generator
82:(fig.1, 2, 3, 4)
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829:Mersenne's laws
763:Audio frequency
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721:Psychoacoustics
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604:Further reading
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936:Related topics
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451:Chladni plates
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431:chart recorder
423:(right center)
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269:longitudinally
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252:boundary layer
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179:standing waves
151:attached to a
123:The tube is a
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113:standing waves
101:speed of sound
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41:the key points
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882:Ernst Chladni
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844:Standing wave
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812:Inharmonicity
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679:Soundproofing
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674:Reverberation
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485:(in German).
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927:Thomas Young
877:Jens Blauert
865:Acousticians
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532:. Retrieved
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506:. Retrieved
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208:in the air:
205:
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197:
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170:
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155:producing a
122:
119:How it works
97:August Kundt
89:Kundt's tube
88:
87:
81:
77:
71:
52:
36:
34:lead section
897:Franz Melde
872:John Backus
856:Subharmonic
709:Spectrogram
457:Rubens tube
419:microphones
175:sound waves
149:loudspeaker
125:transparent
958:Ultrasound
948:Infrasound
734:Bark scale
534:2009-06-25
508:2009-06-25
464:References
191:wavelength
181:, and the
168:wavelength
137:lycopodium
93:acoustical
1014:Acoustics
839:Resonance
739:Mel scale
669:Monochord
648:Acoustics
611:Page 119+
371:λ
361:λ
343:λ
328:λ
225:λ
183:amplitude
164:resonance
157:sine wave
145:resonator
141:pure tone
39:summarize
1008:Category
993:Category
834:Overtone
802:Harmonic
555:(1903).
445:See also
55:May 2014
780:Formant
491:Bibcode
271:at its
173:of the
973:Violin
807:Series
589:
565:–117.
131:dust,
968:Piano
953:Sound
767:pitch
729:Pitch
427:nodes
365:metal
332:metal
301:metal
265:rosin
187:nodes
109:solid
107:or a
103:in a
943:Echo
849:Node
775:Beat
765:and
587:ISBN
133:talc
129:cork
563:115
499:doi
487:127
375:air
347:air
311:air
135:or
105:gas
1010::
543:^
526:.
497:.
481:.
436:.
640:e
633:t
626:v
613:.
595:.
537:.
511:.
501::
493::
390:d
387:L
382:=
355:=
339:f
324:f
318:=
307:c
297:c
281:d
277:L
228:f
222:=
219:c
206:c
202:f
198:λ
194:λ
171:λ
84:.
57:)
53:(
43:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
