The calculation of the transient near and far field of a baffled piston using low sampling frequencies

A method is presented to calculate the near- and far-field transient radiation of acoustical transducers using low sampling frequencies. The method is based on the classical impulse response approach and on the fact that in practical use the spectrum of the excitation function of a transducer is band limited. This makes it possible to use a smoothed version of the impulse response function. A simple expression to calculate this smoothed function, for a rectangular or circular transducer, is derived. The proposed solution allows accurate computation of pressure fields and backscatter signals, while avoiding high sampling frequencies in the far field of the transducers. Several examples illustrate the accuracy of this new solution and its use for spectral analysis of simulated reflected signals.