# Sound Waves: Intensity

1. Feb 14, 2008

### Eternalmetal

1. The problem statement, all variables and given/known data
The intensity at a distance of 6.0m from a source that is radiating equally in all directions is 6.0x10^-10 W/m^2. What is the power emitted by the source?

They give you multiple choice answers, and the answer is 2.7x10-7 W.

2. Relevant equations

I is proportional to 1/r^2.

B = 10log(I/10^-12)

3. The attempt at a solution

I dont really know how to approach getting the solution, I have tried working backwards from the solution and kind of got nowhere. I see no reason to use the decibel formula because there is no need to indicate loudness, so the only other formula I have to work with is a proportion. Could somebody please help me with the formulas/logic needed to solve this problem? I have a terrible professor and my book is no help. Thanks.

2. Feb 14, 2008

### Eternalmetal

Bump. I still need help with this, I put in a bunch of time and im still lost. I would really appreciate a formula or concept explanation or anything, I have the answer but I just want to know how to do it.

3. Feb 14, 2008

### salman213

I dont know but since u havent got a reply im just guessing..

there is some formula i cant remember it is something like...

I =p/4pieR^2

P= I(4)(pie)(r)^2 that gives u like 2.7 x 10 ^-6 W

so it might be wrong and i guess it is since u gave teh answer already but find the power formula and it should be as simple as plugging in..