BEL (B)

A unit of measure of ratios of power levels, i.e., relative power levels. Note 1: The number of bels for a given ratio of power levels is calculated by taking the logarithm, to the base 10, of the ratio. Mathematically, the number of bels is calculated as B = log 10 ( P 1 / P 2 ) where P 1 and P 2 are power levels. Note 2 : The dB , equal to 0.1 B, is a more commonly used unit.