Decibel (dB)

A standard unit used to express a relative measurement of signal strength or to express gain or loss in optical or electrical power. A unit of measure of signal strength, usually the relation between a received signal and a standard signal source. The decibel scale is a logarithmic scale, expressed as the logarithmic ratio of the strength of a received signal to the strength of the originally transmitted signal. For example, every 3dB equals 50 percent of signal strength, so therefore a 6dB loss equals a loss of 75 percent of total signal strength. See Chapter 1 for more information.