Figure 1. (a) Experimental setup: (1) sand mold, (1b) pouring basin, (1c) feeder, (2) acoustic radiator,
(3) waveguide, (4) booster, (5) transducer 20 kHz; (b) Geometric model where V#1 to V#3 correspond
to the positions for sample characterization (Note: mirrored symmetry).