Perturbation characteristics of ambient sea noise field caused by submerged object

Based on the source model with Gaussian-correlation amplitude,using the integral expressions for any source distribution and the spherical wave expression of Green function for a monopole in a half-infinite space,the perturbation characteristics of ambient sea noise field caused by scattering of the object is discussed theoretically.For a rigid spherical object under the irradiation of monopole and dipole sources,the expressions of direct-arrival noise field,scattering field, total field,and the covariance between the direct-arrival noise fields,the scattering noise fields and the total noise fields at two receivers are obtained,and the numerical results of scattering directional patterns of rigid spherical object and the visibility are given.It is shown that the total noise field is affected not only by the impedance characteristics of object, the direction of receiver,but also by the correlation between surface sources,and the interference between direct-arrival and scattering fields greatly.The results show that the sound visibility of rigid spherical object is about 4~5dB in near range and the scattering directivity characteristics of rigid spherical object under the irradiation of surface sources are different from plane wave incidence.