Directivity factor

urn:mrn:iala:dic:3-1-0145

Directivity factor (of a sound source)

The ratio of the square of the radiated free field sound pressure at a fixed point on the principal axis to the mean square pressure averaged over the surface of a sphere passing through the fixed point and concentric with the source.

Reference: I.E.C. (modified)

Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)

English

charge current

Intensity

Illuminance

Energy

Contrast

Celsius (previously Centigrade)

Capacitance

International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM