LOCAL SPECTRUM OF UNDERWATER AMBIENT NOISE FIELD

<正> The radiation of the ambient noise sources on the sea surface is expressed as a superposition of random plane waves. The statistically space-time fine structures of the noise field produced by the radiation of the noise sources in layered inhomogeneous medium are studied.In this paper the concept of local spectrum of the ambient noise field is introduced and a function L(z) which characterizes the space length of the statistical inhomogeneity of the ambient noise field is defined. A physically clear formula of the local spectrum relating to the characters of the noise sources and to the propagation conditions is obtained. By using the formula, the space-time correlation function and the local directional function of the ambient noise field are discussed in detail.It is found that the interesting "low noise channel" exists in several cases.