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Homework Help: Sound Intensity level problem

  1. Jan 21, 2010 #1
    1. The problem statement, all variables and given/known data
    What fraction of the acoustic power of a noise would have to be eliminated to lower its sound intensity level from 90 to 70dB?

    2. Relevant equations
    I = Power/Area
    B = 10 * log *(I/I0)

    I0 = 10-12W/m2

    3. The attempt at a solution
    The answer I got for this is that the new power is 1% of the original. Which I don't think is true. A nudge in the right direction would be appreciated
  2. jcsd
  3. Jan 21, 2010 #2
    You can just solve [itex] B = 10 * log (I/I_0) [/itex] for I with B=90 and B is 70

    remember to use the base 10 logarithm and not the natural logarithm
  4. Jan 21, 2010 #3
    Thanks. I guess it is 1% of the original power after all. Seems kind of strange that it would have to drop so dramatically for only 20dB.
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