(des’ ∂ b∂l) A unit used in expressing power or intensity ratios: 10 log10 of the power ratio. An amplitude ratio of 2 (which represents a power ratio of 4) is equivalent to 6 dB. Also expressed as 20 log10 of the amplitude ratio. See also Figure D-3. 1 dB=0.1151 neper. Named for Alexander Graham Bell (1847–1922), inventor.