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## Homework Statement

Decibel level from source at 1.0 m is 60.0 dB

Find dB level at distance 2.0 m.

## Homework Equations

dB = 10 log

_{10}(I/I

_{0}) <- this one I know but couldn't see an application.

Forgot to add that I

_{0}is equal to 1.0 x 10^-12 W/m^2

dB = dB

_{i}- 20 log

_{10}(r

_{2}/r

_{1}), where r

_{2}is the farther sound source and r

_{1}is the closer one.

## The Attempt at a Solution

I arrived at the correct answer of 54.0 dB by using the looked up formula. But I'd rather know how to derive that formula that relates the source distances myself. I tried for a while but am unable to do it. Anyone able to give me some insight on how to arrive at the second formula?