bel - technical definition

In physics, a measure of comparative power ratio, or relative loudness. In other words, a unit of power ratio. The number of bels is the decimal logarithm of the power ratio, which is expressed mathematically as follows: B = log 10 (P 1 /P 2 ) where B = Bel, and P 1 and P 2 are power levels. One bel is equal to 10 decibels. The bel is named for Alexander Graham Bell, inventor of the telephone, among other things. See Bell, Alexander Graham; decibel; logarithm; and power.