Pronunciation: (des'u-bel", -bul),[key] —n.Physics. 1. a unit used to express the intensity of a sound wave, equal to 20 times the common logarithm of the ratio of the pressure produced by the sound wave to a reference pressure, usually 0.0002 microbar.
2. a unit of power ratio, the number of units being equal to a constant times the logarithm to the base 10 of the intensities of two sources.
3. a unit used to compare two voltages or currents, equal to 20 times the common logarithm of the ratio of the voltages or currents measured across equal resistances. Abbr.: dB, db