level in decibels equal to ten times the logarithm to the base ten of the ratio of the backscattering coefficient of the volume to the reference volume backscattering coefficient 4π/r0, where r0 is the reference distance, preferably chosen to be 1 m
Note 1 to entry: Whatever reference coefficient is used, it shall be specified.
Note 2 to entry: The volume scattering differential for a designated direction other than backward is similarly defined.
Note 3 to entry: Otherwise described, the volume backscattering differential is the backscattered sound pressure level that would exist at the reference distance of r0 from the acoustic centre of the volume containing scatterers, minus the sound pressure level of a plane wave incident on the scatterers.
Note 4 to entry: Expressed in letter symbols:
where:
NV is volume backscattering differential or volume scattering strength
LSC is backscattered sound pressure level at reference distance
Li is incident sound pressure level
AV is backscattering cross-section of scatterers in volume V
r0 is reference distance
is reference volume
m = AV /V is volume backscattering coefficient
is reference volume backscattering coefficient.
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