ˈdesəˌbel, -_bəl noun
( -s )
Etymology: International Scientific Vocabulary deci- + bel
1. in electronic communications
a. : a unit for expressing the ratio of two amounts of electric or acoustic power equal to 10 times the common logarithm of the power ratio — abbr. db
b. : a unit for expressing the ratio of the magnitudes of two electric voltages or currents or analogous acoustic quantities (as sound pressure or particle velocity) equal to 20 times the common logarithm of the voltage or current ratio provided that the two voltages or currents are measured on equal resistances
2. : a unit for measuring the relative loudness of sounds equal approximately to the smallest degree of difference of loudness ordinarily detectable by the human ear the range of which includes about 130 decibels on a scale beginning with 1 for the faintest audible sound