Acoustic Imaging in Four-layer Medium by Iterative Bayesian Focusing Algorithm

A layered medium is studied in this paper. The considered layered medium is divided into four layers in the vertical direction according to the variation of the sound speed, which is a constant or changes linearly in each layer. The sound speed does not change (or changes slowly) in the horizontal direction. The wave equation has no analytical solution owing to the irregular variation of the sound speed. In the forward model, the spectral element method is used for numerical simulations to get the numerical solution of the wave equation, which is implemented by performing a full-wave simulation in the time domain. The iterative Bayesian focusing algorithm is applied to implement acoustic imaging in the inverse problem. Finally, a numerical simulation is designed to validate the four-layer model and the acoustic imaging algorithm. The simulation results demonstrate that the iterative Bayesian focusing algorithm has accurate localization effects and reconstruction results in the four-layer model and its comparison with the conventional beamforming algorithm.