You measure the intensity of a sound wave to be 9.80 w/m2 . the power output of the signal is 75 w and the signal is emitted in all directions.

part a

how far away from the source are you?

r = ?

r = 0.78 m

Explanation:

If the sound source is emitting the signal evenly in all directions (as from a point source) this means that at any time, the source power is distributed over the surface of a sphere of radius r.

At a distance r of the source, the intensity of the sound is defined as the power per unit area:

I = P/A

As the area is the area of a sphere, we can say the following:

I = P / 4*π*r²

Replacing I and P by the values given, we can solve for r (which is the distance from the listener to the source) as follows:

r² = P / I*4*π ⇒ r = = 0.78 m

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