Decibel  --  A unit of level equal to ten times the logarithm of the ratio of two powers. Depending on the reference level used, the decibel symbol will be immediately followed by a letter, as: dBA - An "A" weighted decibel level. dBB - A "B" weighted decibel level. DBC - A "C" weighted decibel level. dBm - A decibel level in which Pb represents one milliwatt of power dissipated in a 600 ohm line. Pa must a also be measured in a 600 ohm line. DBV A decibel voltage level, in which the reference, Vb, is 1.0 volt. A reference of 0.775 volts is also frequently used. 

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