EXPERIMENTAL STUDY OF THE INFLUENCE OF SPATIAL INHOMOGENEITIES IN UNDERWATER ACOUSTIC PROPAGATION

Abstract

International audienceThe authors investigate here the problem of acoustic wave transmission through a spatially fluctuating medium. Although experimental and analytical study are available in the literature, the objective is here to reproduce in tanks some phenomena, such as linear internal waves, that are responsible for horizontal fluctuations of the depth dependant sound speed profile and de-coherence effects of the propagated acoustic signals. The idea is to use acoustic lenses, or wax plates presenting a specific profile, to obtain ultrasonic pressure fields comparable to what can be observed in the case of lower frequency acoustic wave travelling through linear internal waves. Analytical studies allowing to compare dimensionless quantities relative to the measured field with Flatté's classical typology are developed as a support for the experiment. We believe that being able to reproduce these phenomena in controlled environment will be of great help not only to understand and anticipate the perturbations observed on the acoustic wave fronts, but also to work on some corrective signal processing techniques. We focus here on the observation of the wave fronts of the perturbed signals and on the influence of the perturbations on a focalization algorithm