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;{rm W}/{rm m}^{2}.

a). An intensity of 1.0;{rm W}/{rm 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?

Express your answer using two significant figures.