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Homework Help: Calculating sound Intensity?

  1. Apr 23, 2010 #1
    During my lecture we were presented with this problem

    How much louder is the intensity of sound at a rock concert in comparison with the sound of a whisper, if the two intensity levels (in dB) are 120 and 20, respectively?

    What my professor said was that the rock concert was 100 dB greater than the whisper because

    120dB-20dB = 100dB and thus 1010 times louder, but I can't get the math to work out properly.

    I did

    100dB = 10log(I/10^-12)

    10 = log(I/10^-12)

    10^10 = I/10^-12

    I = 0.01
  2. jcsd
  3. Apr 23, 2010 #2


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    Homework Helper
    Gold Member

    Perhaps you forgot the superscript, but I believe you instructor probably said it's 1010 times louder, not 1010 times louder. (1010 would be correct.)

    Your calculations might correspond to the intensity that is 100 dB louder than the human threshold of hearing (depending on which units you are using for your 10-12 figure). But your instructor claimed that the concert was 100 dB louder than a whisper. :smile:
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