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Homework Help: Ratio of amplitudes of sound problem

  1. May 27, 2006 #1
    Sir,
    The intensity level due to 2 waves of same frequency in a given medium is 1 bel and 4 bel. What is the ratio of their amplitudes?
    I solved it in the following way:
    L1 = 10 decibels
    L2 = 40 decibels
    Loudness(L) = 10(log(I/Io))
    Where I= Intensity of sound, Io = Intensity of weakest audible sound
    Therefore,
    10 = 10[log(I1/Io)]
    Similarly,
    40 = 10[log(I2/Io)]
    Solving we get,
    I1 = 10 Watt/m^2
    I2 = 10000 watt/m^2
    Intensity is proportional to (amplitude)^2
    I1/I2 = a1^2/a2^2
    a1/a2 = [I1/I2]^(1/2)
    i.e. a1/a2 = [1/1000]^(1/2)
    = 1/[10^(3/2)]
    Is it right?
     
  2. jcsd
  3. May 27, 2006 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Sounds good to me.
     
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