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Homework Help: Pain from Horn Sound.

  1. Apr 13, 2012 #1
    Pain from Horn Sound. (Solved Already)

    1. The problem statement, all variables and given/known data
    At a distance of 15 km, a 110 Hz horn, assumed to be a point source, is barely audible. At what distance would it begin to cause pain?

    2. Relevant equations
    1.)I(4 pi R^2) = I2 (4 pi R2^2)
    2.)P= I(4 pi R^2); power at the point source

    3. The attempt at a solution
    Using the two equations above I set it so that my equation looks like the first one and then tried to solver for R2. I believe "I" should be equal to 10x10^-12 and the I2 should be equal to 1 because it's the pain threshold.

    From there R in meters would be 15000 and I tried solving for R which lead me to the equation:
    sqrt((1*(4*pie*15000^2))/(4*pie)) which lead me to the answer of: .04743m. Which is wrong. Any help?

    EDIT: Nevermind I found the answer to it already.
    Last edited: Apr 13, 2012
  2. jcsd
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