Calculating Sound Energy from Isotropic Loudspeaker

[Jtappan]

1. Homework Statement

The sound level 24 m from a loudspeaker is 66 dB. What is the rate at which sound energy is produced by the loudspeaker, assuming it to be an isotropic source?

____W

2. Homework Equations

?

Something to do with Intensity?

3. The Attempt at a Solution

I don't know where to begin on this problem. My book doesn't describe any problems that are related to distance nor does it have any equations that are related to distance.

 

[dwintz02]

First, convert the 66dB to Watts. (http://en.wikipedia.org/wiki/Decibel) look in the example section if you don't know how to do that. This will give you the energy rate 24m away.

Next, you'll need to find some formula which relates how energy falls off with distance...any ideas? Look in your book for a formula with (distance)^2 in the denominator.