The difference-frequency acoustic scattering from nonlinear objects

The difference-frequency acoustic scattering from nonlinear objects such as bubbles was studied for many years and used for bubble diagnostics. In the present paper we consider theoretically two problems. The first one is the difference-frequency scattering from the nonlinear layer in linearly stratified medium. The second problem is the difference frequency scattering from the system of periodic nonlinear layers. In both problems the resonance phenomena are studied and their influence on characteristics of the scattered fields are analyzed. In the third part of the paper we describe experimental method of acoustic difference-frequency vision of large-scale bubbly objects.