Directional gain (of a sound source, in decibels)
Alternative term: Directivity index (of a sound source, in decibels)
Ten times the logarithm to the base 10 of the directivity factor.
Reference: I.E.C. (modified)
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)
Celsius (previously Centigrade)
International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM