Time-frequency Analysis of Broadband Sound Pulse Propagation in 3-d Oceanic Waveguides

When considering low-frequency sources, the oceanic environment can act as a very dispersive waveguide, especially in shallow-water long-range sound wave propagation. One efficient tool for studying dispersion effects is based on time-frequency (TF) analysis of the received signals using a single receiver [1,2] . However, theses studies only considered two-dimensional (2-D) waveguides. In the present paper, TF analysis is used to study the propagation of low-frequency broadband pulses in three-dimensional (3-D) shallow-water waveguides. In particular, the paper focuses on the 3-D ASA wedge benchmark for which the received signals present characteristic modal structures including multiple mode arrivals. Indeed, it is well known that, due to the presence of a tilted bottom, a single propagating mode can have two distinct arrivals on a single receiver located in the across-slope direction. One objective of the present study is to show that TF analysis can be a suitable tool to better understand and easily illustrate this phenomenon.