Intensity Difference in dB

Two signals with intensities $I_1$ and $I_2$ may be compared by expressing in decibels:

$$\textcolor{blue}{ \Delta L = 10\log I_2/I_1 \mbox{ dB}. }$$

When decibels are used as absolute measurements, there is an implied reference (e.g. threshold of audibility):

$$\textcolor{blue}{ L_I = 10\log I/I_0 \mbox{ dB}, }$$

where $I_0 = 10^{-12}$    W/m$^2$.