Images of the experimentally determined transducer radiation patterns are shown in the first column. In the second column, theoretically determined transducer radiation patterns are shown. Line plots through the center of the experimental data (black dashed lines) and the theoretical data (blue solid lines) are shown in the third column. The first row corresponds to a propagation distance of 11.76 cm (the location of an intensity maximum on the optical axis in the near zone). The second row corresponds to a propagation distance of 17.67 cm (the location of an intensity minimum on the optical axis in the near zone). The third row corresponds to a propagation distance of 35.36 cm (the near-zone/far-zone transition distance). The fourth row corresponds to a propagation distance of 49.36 cm (a distance in the far zone).
