decibel -
A common measure of sound intensity that is one tenth of a bel on the logarithmic intensity scale. It is defined as dB = 10 * log10P 1/P 2, where P1 and P2 are the relative powers of the sound.
Wikipedia
The decibel (dB) is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities. Being a ratio of two measurements of a physical quantity in the same units, it is a dimensionless unit.
OmegaWiki Dictionary
Ω
decibel A unit used to express relative difference on power, usually between acoustic or electric signals, equal to ten times the common logarithm of the ratio of the two level.
