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.