An Etymological Dictionary of Astronomy and Astrophysics

A dimensionless unit used to express relative difference in power or intensity, usually between two acoustic or electric signals. It is defined as n [dB] = 10 log (P₁/P₀),
with → natural logarithm. One decibel equals one-tenth of a → bel (B).

See also: → deci-; → bel (B).