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Homework Help: Sound Intensity

  1. Apr 14, 2008 #1
    1. The problem statement, all variables and given/known data
    The amplitude of a soundwave is 5 X 10 ^-5 N/m^2
    a) What is the intesity of the sound energy from this sound wave?
    b) What is the sound level?

    3. The attempt at a solution

    Well I believe that Sound intensity is Power/amplitude. However, i only have the amplitude so.. does that mean that my problem is impossible?
  2. jcsd
  3. Apr 28, 2008 #2
    L (dB) = 20*Log(P/Pref) = 10*Log(I/Iref)

    According to the units, you are given the pressure (50 uN/m^2 = 50 uPa). Sound Pressure Level is 20*Log(P/Pref) where Pref is 20uPa. You get around 8 dB.

    Sound Intensity = Sound Power / ***Area***. Now this 8 dB is just a ratio and is also equal to 10*Log(I/Iref) where Iref is 10^-12 W/m^2. You get 6.3*10^-12 W/m^2.
  4. Apr 28, 2008 #3
    OH. Thanks for your solution. I realize that I made a complete blunder now. So it was my formula...I get it now, but that does not bode well for my test results =|. Thanks again for your help.
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