divergence loss

5.38  divergence loss; spreading loss. That part of the transmission loss resulting from divergence of sound waves in accordance with the geometry of the system (e.g., spherical waves emitted by a point source). Unit, decibel (dB).

Annotation              For spherical waves, time-mean-square sound pressure varies inversely as the square of distance from the source; for cylindrical waves, time-mean-square sound pressure varies inversely as distance from the source.