THE USE OF BACK PROJECTION RECONSTRUCTION OF ACTUAL SOURCE CHARACTERISTICS FOR A RADIATING TRANSDUCER IN NONLINEAR PRESSURE FIELD MODELLING

摘要

Nonlinear distortions during the propagation of a finite-amplitude acoustic wave in a dissipative fluid are frequently studied in the nearfield of a sinusoidally excited, circular piston source using a planar receiving transducer with a diameter equal to that of the source. In the paper direct numerical solutions of the nonlinear parabolic KZK equation are used to determine the averaged acoustic pressure on the receiving transducer. The technique allows a precise modelling of the combined effects of diffraction, absorption and nonlinearity and what is more it takes into account the actual source characteristics of a radiating transducer. The features of the parabolic model are demonstrated through a comparison with an experiment conducted in distilled water for the first four harmonic components of the averaged pressure. The backward projection of the measured acoustic field is employed to reconstruct the source characteristics for the applied transducer. Some results of performed calculations and measurements are given to illustrate the method's capability.