# Homework Help: Sound Intensity level problem

1. Jan 21, 2010

### LeakyFrog

1. The problem statement, all variables and given/known data
What fraction of the acoustic power of a noise would have to be eliminated to lower its sound intensity level from 90 to 70dB?

2. Relevant equations
I = Power/Area
B = 10 * log *(I/I0)

I0 = 10-12W/m2

3. The attempt at a solution
The answer I got for this is that the new power is 1% of the original. Which I don't think is true. A nudge in the right direction would be appreciated

2. Jan 21, 2010

### willem2

You can just solve $B = 10 * log (I/I_0)$ for I with B=90 and B is 70

remember to use the base 10 logarithm and not the natural logarithm

3. Jan 21, 2010

### LeakyFrog

Thanks. I guess it is 1% of the original power after all. Seems kind of strange that it would have to drop so dramatically for only 20dB.