Hello! I am doing some questions about sound waves for my homework assignment and have some problem in one of them.(adsbygoogle = window.adsbygoogle || []).push({});

Assuming that it radiates sound uniformly, find the sound power from a motor car whose sound level at a distance of 7.5m is 87dB.

Here are my steps:

I = sound intensity, I_0 = minimum audible intensity

By h = 10log(I/I_0)

87 = 10 log (I / 10x10^-12)

I = 5.01 x 10^-4 W/m^2

By I = P / 4 pi r^2

5.01x 10^-4 = P / 4 pi 7.5^2

P = 0.354W

But the answer given by my teacher is 0.18W...Can anyone tell me what's wrong in my calculation. Thanks!

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# Homework Help: Find the sound power

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