PROPAGATION EN MILIEU MARIN ALÉATOIRE

Propagation in a deterministic medium is now well known and there exists several methods to investigate the sound field in a deterministic ocean ( geomemc rays, normal modes, parabolic approximation). But, medium isn't so perfect and waves are scattered by medium or surface inhomogeneities. and reflection on bottom. That leads to stochastic changes in the amplitude and phase of waves. So we have to consider the acoustic sound field as a random variable created by random data. First environnemental phenornena are rewieveù in order to define the random data considemi in the following study. Then, a stochastical approach is developed. This approach allows calculating the mean field and the vertical mutual coherence. Based on modal expansion and parabolic approximation its interest results in the fact that phase is taken into account, and so it permits observation of coherent effects. At last we present a statistical approach which wnsists in the resolution of a great number of deterministic problerns that will be averaged to obtain the desireù statistics