Perturbations of Modal Attenuation Coefficients and Group Velocities due to Depth Variations along a Shallow-Water Acoustic Track

Abstract

Perturbations of attenuation coefficients and group velocities of acoustic modes is considered in a shallow-water waveguide with an inhomogeneous bottom relief. Explicit formulas are constructed for calculating the first and second derivatives of the aforementioned quantities with respect to the sea depth on the basis of the perturbation theory developed by the authors in previous publications. Application of the proposed formulas is illustrated by a model example. It is shown that they allow highly accurate approximation of depth dependences for group velocities and modal attenuation coefficients. The proposed formulas can be used to obtain simple analytic estimates of acoustic propagation loss in irregular waveguides, as well as to allow for inhomogeneities of the bottom relief in geoacoustic inversion according to the data on waveguide dispersion of signals.