Acoustic Scattering from Interaction of Dual Frequency Incident Fields

The pressure field produced by the spatial interaction of two high frequency incident plane waves in a three-dimensional scattering object is investigated. Of particular interest is the field produced in response to the difference-frequency component generated from the non-linear interaction of the two harmonically time varying acoustic beams in a high contrast medium. The scattered pressure at the difference frequency field has been shown to enhance the identification of abnormal biological tissue in recent medical ultrasound experiments. This work presents a computational study of the scattered pressure that results from the Reynolds stress in a fluid scatterer. Using Pade approximants, it is shown that the stress tensor can be computed using a uniform expansion in the contrast gauge for the scattered pressure. This allows one to investigate scattering volumes characterized by high compressibility contrast.