Sound Intensity is used to determine the intensity of sound waves. It has the units of decibel. We use the formula:
I(L) = 10log (I / Io)
We use Io equal to 10^-12 W/m2. We calculate as follows:
I(L) = 10log (1 W/m2 / 10^-12 W/m2) = 120 dB
I(L) = 10log (0.001 W/m2 / 10^-12 W/m2) = 90 dB
Therefore, the difference between the sources would be 30 decibels.