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Homework Help: Why does sound pressure vary with 1/r?

  1. Oct 11, 2011 #1
    I didn't follow the template because this is more of a conceptual question that I can't get a clear answer for.

    I understand that sound intensity varies with 1/r^2 because the total intensity at a point in the wave is constant and if you have spherical propagation then the area of the surface of that sphere increases with r^2.

    I can also calculate pressure from the formulas of intensity that include pressure.

    But can anybody give an intuitive explanation for why pressure drops off with distance and not distance squared? Since sound is a travelling pressure wave, I suppose we can pretend that we are riding a pressure peak out in space along a ray.

  2. jcsd
  3. Oct 12, 2011 #2
    The force of a compressed spring is F = kx and the energy in a compressed spring is kx^2/2

    Can you convince yourself that a gas acts like a compressible spring?
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