Pulse-echo single frequency acoustic nonlinearity parameter (B/A) measurement

A pulse-echo single-frequency method for B/A measurement is reported. The technique is based on excitation of the medium at a progressively increasing amplitude level and the computing of B/A from the deviation in linearity of the transducer input-output relationship. Starting from the nonlinear wave equation, a three-dimensional analytical formulation that predicts the approximate field distribution for finite-amplitude waves is derived. This provides the computation for the transducer output voltage for progressively increasing signal levels. It is shown that, by a suitable normalization, the effects of the diffraction can be excluded. From a nonlinear least-squares fit of the experimental data to the analytical equation, the B/A is computed. A number of simulations for the model together with preliminary experiments that were carried out at 3.5 GHz are presented.<>