DB (DECIBEL)

The standard unit used to express gain or loss of power along a signal path. It indicates the logarithmic ratio of output power divided by input power. A power loss of 3 dB is an attenuation of the incoming signal by half of its original value. A 3 dB power loss is equal to a 6 dB voltage loss. [dB = 10 log P1/P2, P = V¨/R, If R is a fixed value, then: dB = 10 log (V1/V2)¨ or dB = 20 log V1/V2. ] This method of scaling levels becomes important because human sensitivity to sight and sound are logarithmic, which accounts for our large dynamic range capability.