Re: [Phys-L] Quincke tube acoustic interferometer apparatus
Larry Smith asked several questions of which I address only this one:
Do you have any insights on why we got so many resonances?
'Single tube standing waves' is another way of describing harmonics, so in a
tubethere is a ladder of ascending resonances. One way of decreasing the
amplitude of harmonics is to keep the wave as near a sine as possible.If the
sound source amplitude is limited only by physical stops, the square wave
resulting is rich in harmonics.One way of decreasing the number of resonances
at higher anharmonic frequencies is to reduce the effect of discontinuities in
the acoustic pathway ('acoustic impedance steps') of which the most obvious is
the tee junction into two pipes of different lengths.
It is notable that Randall & Boot who created the cavity magnetron, used sound
as an aid in developing the source and pathway of their 500 watt prototype
microwave generator.at Birmingham University. This helped them discover
effective methods of creating and transmitting the oscillation along a pipe
('waveguide') without the crippling losses out of previous structures such as
the glass envelope created by Hull at GE Research Lab 20 years earlier On
Tuesday, December 12, 2023 at 04:57:04 PM CST, Larry Smith
<larry.smith@snow.edu> wrote:
Phys-L:
We built an “acoustic interferometer” (a.k.a. “Quincke tube”?) much like the
one shown in Figure 18.5 on p. 548 of Serway and Jewett’s “Physics for
Scientists and Engineers” 6th ed. We designed an experiment much like the one
shown in the first video of
https://instructional-resources.physics.uiowa.edu/demos/3b5540-interference-quinckes-tube-or-trombone
However, when we ran the experiment ourselves before foisting it on the
students we found many more resonances (ramping up the frequency for a given
∆r) than simple path length difference would predict. We wonder if we are also
getting single-tube standing waves.
Has anyone run a successful acoustic interferometer lab with students?
Are you willing to share?
Do you have any insights on why we got so many resonances?
Is Quincke tube the right name for this?
Thanks,
Larry
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