Directivity Patterns in Inhomogeneous Acoustic Media

Abstract

Acoustic sources directivity patterns in homogeneous liquid media where the waves propagation velocity is constant everywhere, are determined by the well know diffraction formulae¹. In such a medium it is possible to focus the wave as well as to reconstruct an image based on delay or phase processing of radiated or received waves. However, most of the media in which acoustical imaging is performed are, in fact, inhomogeneous. The propagation velocity varies from point to point in human tissues, under water as well as in soil. It leads, in some cases, to phase perturbations of propagating wave that can deform directivity patterns as well as limit focussing possibilities and, in the case of strong inhomogeneities, make impossible any image reconstruction of objects submerged in the medium.