Note 1 to entry: Whatever the reference area used, it shall be specified.

Note 2 to entry: The object scattering differential for a designated direction other than backward is similarly defined.

Note 3 to entry: Otherwise described, the object backscattering differential is the backscattered sound pressure level that would exist at the reference distance of r₀ from the acoustic centre of the scattering object, minus the sound pressure level of a plane wave incident on the object.

Note 4 to entry: Expressed in letter symbols, the definition reads:

${\displaystyle N_{\text{ts}}=L_{\text{SC}}-L_{\text{i}}=10{\text{log}}_{10}\frac{A_{\text{ob}}}{4\pi r_0^2}\text{dB}}$

where:
N_ts is object backscattering differential or target strength
L_SC is backscattered sound pressure level at reference distance
L_i is incident sound pressure level
A_ob is backscattering cross-section of object
r₀ is reference distance
$4\pi r_0^2$ is reference area for object backscattering differential.