Simulation of the Nonlinear Acoustic Field Generated by a Concave Spherical Transducer in Multi-layer Mediums

We simulate the acoustic field generated by a concave spherical transducer by using two different models. One model consists of two mediums and the other is comprised of four mediums. It is found that the nonlinear effects are affected by excitation frequency, radiation intensity, half-aperture angle and medium thickness, and behaves relatively stronger in the focusing point and the interface where two adjoining mediums have larger discrepancy of nonlinear parameter value. As the excitation frequency increases, the nonlinear effects will enhance in the interface but lower in the focus. In focal region the nonlinear effect becomes remarkable with increasing the acoustic intensity on the source face and has some drop while the half-aperture angle widens. When the medium with largely nonlinear parameter value becomes incrassate, the nonlinear effect weakens and the sound pressure reduces.