Figure 2.

Pressure profiles of the apodized dual-element Sonic Concepts H105 transducer. Point spread function calculations of the dual-element H105 transducer is shown as pressure profiles (a) before and (b) after apodization. The pressure delta over the radiating surface can reach up to 4 dB in the non-apodized configuration (shown in a), but is greatly reduced to 1.7 dB after apodization by driving the outer element at 50% electrical amplitude of the inner element (shown in b). (c) A hydrophone was used to measure the actual pressure coming from the H105 transducer at a distance of 1 mm from its face. Relative pressure is encoded in color: warm colors indicate higher acoustic pressures; cool colors indicate lower pressures. Spatial scalars are 70-mm full range in each dimension, with an effective beam footprint of ~21 cm². Although there remain some transaxial inhomogeneities in the pressure field map, as indicated by modest annular structure, the near field of the transducer was remarkably uniform over most of the transducer face.