Effective acoustic centre
Effective acoustic centre (of a sound source)
The point from which the spherical waves as observed at remote points appear to diverge.
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