Instantaneous sound power per unit area
Instantaneous sound energy flux per unit area
The quotient of the instantaneous sound power transmitted across a surface element and the area of the surface element.
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