The possibility of mathematical modeling of ultrasonic beam, the most influencing factor in the ultrasonic methods in quality control of materials and constructions, is considered. We have focused attention on the distribution of acoustic energy in inspected material, since a reliable estimate of the reflector size is possible only if the former is known. In the experimental part we used an ultrasonic pulse-echo method and piezoelectric probes, as well as two basic types of reflectors that cross the ultrasonic beam and the reflectors that are within the beam, as representative for the flaw in inspected materials. In the modeling we have included realin situconditions and factors influencing the results, and the results were selected using the proposed optimal criteria. ©1997 American Institute of Physics.