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Homework Help: Sound moving through different mediums

  1. Oct 9, 2005 #1
    A certain pipe produces a fundamental frequency of f in air.

    If the pipe is filled with helium at the same temperature, what fundamental frequency does it produce?

    I assume that I just take (f/v1)(v2), with v1 being speed in air and v2 being speed in helium

    this lead me to the equation:

    However, this is somehow off by a multiplicative factor. I can, however, find no way in which any other factor would be involved...
  2. jcsd
  3. Oct 9, 2005 #2


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    Assuming that the mechanism in which the sound is being generated remains the same, the frequency does not change. If the speakers are vibrating the air at 5kHz, then changing the air content will not affect how they vibrate.
  4. Oct 9, 2005 #3
    i think this may be assuming that air/he is the medium which the wave is traveling in, not the pipe itself
  5. Oct 10, 2005 #4
    or.. f is also the fundamental frequency of the pipe, so you are using f = nv/2pi (or 4pi) i can't remember which, but that factor of the equation should be inconsequential.
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