Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Ratio of amplitudes of sound problem

  1. May 27, 2006 #1
    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
    10 = 10[log(I1/Io)]
    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.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook