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Confused by canceling sound waves

  1. Mar 6, 2005 #1
    I'm confused by this problem: http://myspace.homelinux.com:32123/sound.jpg [Broken]
    Can someone explain the solution and what's wrong with my reasoning?
    It takes 1.7/340 = .005 sec for the wave to travel the 1.7m. So for the waves to cancel woudn't .005 = T * 1/2 * n (where T is the period of the wave and n is an integer)? Since T= 1/f, we have f = 100n. But then f could be 200hz, 300hz, or 400hz, so that must be wrong... :frown:
    Last edited by a moderator: May 1, 2017
  2. jcsd
  3. Mar 6, 2005 #2


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    For destructive interference, the distance must be an odd multiple of the half-wavelength. If it were an even multiple, that would be constructive interference.
  4. Mar 6, 2005 #3
    oh wow duh that was obvious :blushing: thanks!
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