Fig. 1.

Calibration measurement configurations. (a) Pitch-catch method with two transducers coaxially and confocally aligned, separated by the sum of focal lengths $F_{\text{source}}+F_{\text{PCD}}$. The transmitted wave is measured by the PCD and compared with the spatially averaged pressure amplitude measured by a reference hydrophone. (b) Bistatic scattering substitution method with source and PCD confocally and orthogonally aligned with a spherical scatterer. Scattering of the source's field by the sphere is measured by a PCD centered at scattering angle $\theta ={90}^{°}$ and compared with the pressure measured by a reference hydrophone at the same angle.