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# Sound Intensity and Threshold of pain

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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?

https://brainmass.com/physics/sound-measurement/sound-intensity-threshold-pain-175688

## SOLUTION This solution is FREE courtesy of BrainMass!

I1 = 0.11 W/m^2, I2 = 1 W/m^2, r1 = 7.5 m

To find: r2

The sound intensity from a point source varies inversely as the square of the distance from it.

I1/I2 = (r2/r1)^2

r2/r1 = sqrt (I1/I2)

r2 = r1 * sqrt (I1/I2)

r2 = 7.5 * sqrt (0.11/1) = 2.4875 m

You can safely move closer by another 7.5 - 2.4875 = 5.0125 m (= 5.0 m using two significant figures).

This content was COPIED from BrainMass.com - View the original, and get the already-completed solution here!