In the study, based on the sea noise source model with Gaussian-correlation amplitude, and applying the integral expressions for arbitrary source distribution and the spherical wave expression of Green function for a monopole in half-infinite space, the researchers obtained the expressions of direct-arrival noise fields, scattering fields and total noise fields of a rigid spherical object under the irradiation of monopole and dipole sources, as well as the covariance among those noise fields at two receiving points.

They carry out experiments and the numerical results of scattering directional patterns of rigid spherical objects and the visibility show that the total noise field is affected by not only the impendence characteristics of the object, the directional of receiver, but also the correlation between surface sources, and the interference between direct-arrival and scattering fields greatly. The results show that that sound visibility of a rigid spherical object is about 4-5 dB in near range and the scattering directivity characteristics of a rigid is about 4-5 dB in near range and the scattering directivity characteristics of a rigid spherical object under the irradiation of surface sources are different from those of plane wave incidence.