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# Physics Q?

A person shouting as loud as he can transfers about 1.0W of power into sound waves. What is the sound intensity level (dB) 2.0m from the person? Assume the person emits a spherical sound wave.

### 1 Answer

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- az_lenderLv 77 months ago
The surface area of the sphere is

4*pi*(2.0 m)^2 = 50.3 m^2, so the intensity of the sound is (1 W)/(50.3 m^2) = 2.0 x 10^(-2) W/m^2.

The intensity LEVEL is

10*log_10[intensity/(10^(-12) W/m^2)].

In your problem, it's

10*log_10(2 x 10^10) = 10*10.3 = 103 dB.

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