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Harmonics of a closed-closed tube

  1. Nov 18, 2009 #1
    I don't understand how to get n... if that doesn't make sense i can explain more... I have the length and velocity... from there i just don't understand what n even is or means...
  2. jcsd
  3. Nov 18, 2009 #2


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    n is the mode or the multiple of the fundamental frequency. If you want the third harmonic, n=3.
  4. Nov 19, 2009 #3


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    It should really be referred to as the second (U)overtone(/U) for a physical resonator because the frequencies of overtones may not be exactly harmonically related. Look at the spec of Quartz crystals for use in oscillators and you'll see what I mean; It's all to do with 'end effect' and effective length of the oscillating object, in wavelengths. Having said this, for a closed-closed tube, the end effect will be v. small.

    The fundamental frequency will be the frequency at which there is a half wavelength between the two ends - allowing a node at each end*. The first overtone will be when there is a node in the centre (i.e. at near twice the frequency) and the second will be when there are two nodes - asoasf.

    * fundamental f =c/2x
    where c is the speed of sound in the tube and x is the effective length
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