Logarithm of the ratio of two values of a field quantity, usually amplitude. Levels
are expressed in different ways:

,
where

is the symbol for the unit
neper coherent with the SI, or

,
where

is the symbol for the unit
decibel.
Source:
Cite as:
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by
A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997).
XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic,
J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8.
https://doi.org/10.1351/goldbook.