Quincke's interference tube

Quincke interference tube

A technical work in which the extinction of the sound waves was made visible with the help of an oscilloscope

The Quincke interference tube is a device for the detection of interference phenomena of sound waves . It can also be used to measure acoustic wavelengths . It is named after the physicist Georg Hermann Quincke , who constructed this and other “interference apparatus” in 1866. Due to its simple and clear structure, the Quincke interference tube is a popular demonstration experiment in school physics. In addition to the name interference tube , the name Quincke trombone is used, as the outer shape with the extendable tube is reminiscent of a trombone. However, the way the two devices work is fundamentally different.

construction

The Quincke interference tube consists of two U-shaped tubes inserted one inside the other, which can be pulled apart and together like a trombone. Extension tubes are attached at two opposite points . A tone with a certain frequency is brought into the pipeline via the extension pipe T. At the other extension tube O the sound arriving there is registered with the ear or a microphone.

functionality

The sound travels from the inlet opening T via the pipe bend A as well as the pipe bend B to the outlet opening O. Depending on the path difference, which can be changed by moving the U-tube, the sound is weakened or amplified as a result of interference:

If at a sound wavelength λ is the path difference

{\ displaystyle 2 \ cdot d = n \ cdot {\ frac {\ lambda} {2}}}

With

{\ displaystyle n \ in \ {1,3,5, \ ldots \}}

this results in destructive interference: the two sound waves cancel each other out.

Is the path difference

{\ displaystyle 2 \ cdot d = n \ cdot {\ frac {\ lambda} {2}}}

With

{\ displaystyle n \ in \ {0,2,4, \ ldots \}}

this results in constructive interference: the two sound waves reinforce each other.

With constant lengthening of the path difference, equidistant sound maxima or minima can be measured at intervals of the wavelength λ.

Individual evidence

^ Georg Hermann Quincke: About interference apparatus for sound waves. In: Annals of Physics . Verlag Joh. Ambrosius Barth, Leipzig, 1866, Volume 204, pp. 177–192 plus Plate VI (identical: Poggendorfs Annalen , 1866, Volume 128)

[1] Georg Hermann Quincke: About interference apparatus for sound waves. In: Annals of Physics . Verlag Joh. Ambrosius Barth, Leipzig, 1866, Volume 204, pp. 177–192 plus Plate VI (identical: Poggendorfs Annalen , 1866, Volume 128)