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Homework Help: Sound/Energy problem

  1. Jun 29, 2009 #1
    A sound wave with intensity of 80.1 dB is incident on an eardrum of Area = 0.7x10^-4. How much energy is absorbed by the eardrum in 4 minutes???

    I know this much..... Power = (Intensity)(Area)..so...P=(80.1)(0.7x10^-4)

    and Energy = (power)(time) so....E = (80.1)(0.7x10^-4)(240 sec) = 1.35

    However, this is not the correct answer. Am i not doing the right conversions or what?? What looks wring here? (the correct answer is 1.72)

    I know it probably has something to do with converting dB to something....im just not sure how..
  2. jcsd
  3. Jun 29, 2009 #2


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    Homework Helper

    Isn't a decibel a log of the ratio of the sound to a reference level?

    So ... 80.1 dB = 10log10(P1/Po)

    Po is what? 10-12W/m2 ?
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