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**[SOLVED] sound intensity - the threshold of pain**

**1. Homework Statement**

You are investigating the report of a UFO landing in an isolated portion of New Mexico, and encounter a strange object that is radiating sound waves uniformly in all directions. Assume that the sound comes from a point source and that you can ignore reflections. You are slowly walking toward the source. When you are 7.5 m from it, you measure its intensity to be 0.11 W/m^2.

An intensity of 1.0W/m^2 is often used as the "threshold of pain". How much closer to the source can you move before the sound intensity reaches this threshold?

**2. Homework Equations**

I1/I2 = r2^2/r1^2

**3. The Attempt at a Solution**

r2 = r1(I1/I2)^1/2

= (7.5)(.11)^1/2 = 2.5m - incorrect

done another way

r2 = [(r1)^2(I1/I2)]^1/2 = (56m^2(.11))^1/2 = 2.5m - incorrect

I dont' know the equations aren't working for me, any help is appreciated.