Acoustic noise models

Abstract

The question of modeling the vertical directionality of ambient noise in the ocean is considered. The problem of converting from a description in terms of directional density function to a description in terms of the cross-spectral density function between pairs of sensors of arbitrary orientation and separation is examined in detail. Mathematical models which have been used previously are reviewed with special emphasis on spatial harmonic models following closely some material presented earlier. [Cox, J.A.S.A. 54, 1289-1301, (1973)]. The underlying philosophy is that realistic composite models can be obtained by combining a number of simple models each of which models a single Significant aspect of the noise field. A new harmonic model is presented for the noise field at the axis of the sound channel due to distant shipping when purely refractive paths dominate. Some simple approximations are developed for the cross-spectral density function in fields dominated by distant shipping.