Slope inversion in a single-receiver context for three-dimensional wedge-like environments

Abstract

In a single-receiver context, time-frequency (TF) analysis can be used to analyze modal dispersion of low-frequency broadband sound pulses in shallow-water oceanic environments. In a previous work, TF analysis was used to study the propagation of low-frequency broadband pulses in three-dimensional (3-D) shallow-water wedge waveguides. Of particular interest is that TF analysis turns out to be a suitable tool to better understand, illustrate and visualize 3-D propagation effects for such wedge-like environments. In the present work, it is shown that TF analysis can also be used at the core of an inversion scheme to estimate the slope of the seabed in a same single hydrophone receiving configuration and for similar 3-D wedge-shaped waveguides. The inversion algorithm proposed, based on a masking process, focuses on specific parts of the TF domain where modal energy is concentrated. The criterion used to quantify the match between the received signal and the replicas by a fully 3-D parabolic equation code, is defined as the amount of measured time-frequency energy integrated inside the masks. Its maximization is obtained using an exhaustive search. The method is first benchmarked on numerical simulations and then successfully applied on experimental small-scale data.