A logarithmic measure of the ratio of two signal levels: dB = 20 log (Voltage1 / Voltage2) dB = 10 log (Power1 / Power2)Variants on the decibel (dB) used in spectrum-analysis and network-analysis measurements are dBmV absolute voltage level referred to 1 mVdBµV absolute voltage level referred to 1 µVdBm absolute power level referred to 1 mWdBc level difference referred to a carrier level, c. dBc/Hz level difference referred to carrier level calculated for a measurement bandwidth of 1 Hz. (Spectrum and network analysis.)