Sound interference

  1. Aug 12, 2009 #1
    1. The problem statement, all variables and given/known data

    Two sound waves, from different sources with the same frequency, 540 Hz, travel in the same direction at 330m/s. The sources are in phase. What is the phase difference of the waves at a point that is 4.40 m from one source and 4.00 from the other.

    2. Relevant equations

    We know that [tex]\Phi[/tex] = [tex]\Delta[/tex]L / wavelength * (2pi)
    We also know when the delta L / wavelentgh is a positive integer value, fully constructive interference occurs.

    If delta L/ wavelength is odd integer value then fully destructive interference occurs.

    and then you have your regular kinematics, and dynamics eqns.

    3. The attempt at a solution

    f = 540 Hz, velocity = 330m/s
    f[tex]\lambda[/tex] = velocity
    and we solve for lamda = 540/330 = 1.64 m

    now we plug that into the phase eqn.

    [tex]\Phi[/tex] = [tex]\frac{0.40}{1.64}[/tex]

    that is equal to 0.2439024...

    now i dont know thats my answer, or should i multiply it by 2pi . or what?
  2. jcsd
  3. Aug 12, 2009 #2
    "We know that [tex]\Phi[/tex] = [tex]\Delta[/tex]L / wavelength * (2pi)"

    "[tex]\Phi[/tex] = [tex]\frac{0.40}{1.64}[/tex]"

    You're missing the 2pi.
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