The Diffraction Response Interpolation Method

Computer modeling of the output voltage in a pulse-echo system is computationally very demanding, particularly whenconsidering reflector surfaces of arbitrary geometry. A new, efficient computational tool, the diffraction response interpolationmethod (DRIM), for modeling of reflectors in a fluid medium, is presented. The DRIM is based on the velocity potential impulseresponse method, adapted to pulse-echo applications by the use of acoustical reciprocity. Specifically, the DRIM operates bydividing the reflector surface into planar elements, finding the diffraction response at the corners of the elements, calculating theresponse integrated over the surface element by time-domain convolutions with analytically determined filters, and summing theresponses from the individual surface elements. As the method is based on linearity, effects such as shadowing, higher-orderdiffraction, nonlinear propagation, cannot be directly incorporated in the modeling. The DRIM has been compared to othermodeling tools when possible. Excellent agreement between the results obtained with the DRIM and the alternative techniqueshave been found, and the DRIM offers reductions in computation time in the range from 30 to 400 times. Experimental resultsobtained using a planar circular transducer together with cylindrical reflectors were compared to DRIM results and fairly goodagreement was observed.