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Homework Help: Billy and speakers

  1. Apr 23, 2009 #1
    1. The problem statement, all variables and given/known data

    Two lound speakers are each located 16m from a wall and are 0.8m apart. They play a 3000 Hz sound, both speakers are in phase. Bill is located at the wall at the m=0 maximum of sound interference. If he walks along the wall, how far does he have to walk to hear m=1 maximum? (The speed of sound is 343 m/s.)

    2. Relevant equations

    2pi * (x2-x1) / lambda = 2mpi
    vsound = lambda*f

    3. The attempt at a solution

    343 m/s = lambda*3000Hz
    lambda= .1143 meters

    Beyond that, I do not know how to solve it.
    Thank you.
  2. jcsd
  3. Apr 23, 2009 #2


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    Homework Helper

    Sounds like you have a little geometry problem. Don't you just need to find the point away from the mid-line whose distance from each speaker is different by half a wavelength?
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