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The perturbation characteristics of ambient sea noise field caused by scattering of submerged objects are discussed theoretically.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 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 are obtained.The numerical results of scattering directional patterns of rigid spherical objects and the visibility are given.It is shown that the total noise field is affected by not only the impedance characteristics of the object,the direction of receiver,but also the correlation between surface sources,and the interference between direct-arrival and scattering fields greatly.The results show that the sound visibility of a rigid spherical object 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.
The perturbation characteristics of ambient sea noise field caused by scattering of submerged objects are discussed theoretically. 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 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 are The numerical results of scattering directional patterns of rigid spherical objects and the visibility are given. It is shown that the total noise field is affected by not only the impedance characteristics of the object, the direction of receiver, but also the correlation between surfaces sources, and the interference between direct-arrival and scattering fields greatly.The result s show that the sound visibility of a rigid spherical object 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 from from of of plane wave incidence.