Chapter 1.3.1 - Acoustical Imaging: Classical and Emerging Methods for Applications in Macrophysics

This chapter deals with applications of acoustic wave scattering, starting with a general overview of the subject. Acoustical imaging means imaging with sound. Sound is radiated by a source (speaker, musician, etc.) when modulated in a specific manner, is the vehicle for the transmission of some sort of information from the point of its production (e.g., violin) to the point of its reception. The surroundings are a medium and its boundaries through and off which the sound disturbance will penetrate and be reflected, eventually reaching a real or a virtual listener somewhere outside or inside the medium. The objective in using sound can be much the same as with X-rays provide a picture of the state of the interior (in addition to the envelope) of an object or medium. Brute-force inversion is a way to solve imaging problems at present, fashionable in scientific circles, but does not always convince practitioners in the field. To satisfy the increasingly demanding requirements for obtaining information that goes beyond simple detection is to understand how existing imaging methods work and why they are successful, to search for new, suitable models of the source, the object in its environment and the wave/medium interaction, and to clarify the issue of just what information can be obtained from the pseudo-image, the quasi-image, and the image (for the chosen models).