Geoacoustic inversion on the New England Mud Patch using warping and dispersion curves of high-order modes

Abstract

This paper presents single receiver geoacoustic inversion of a combustive sound source signal, recorded during the 2017 Seabed Characterization Experiment on the New England Mud Patch, in an area where water depth is around 70 m. There are two important features in this study. First, it is shown that high-order modes can be resolved and estimated using warping (up to mode number 18 over the frequency band 20-440 Hz). However, it is not possible to determine mode numbers from the data, so that classical inversion methods that require mode identification cannot be applied. To solve this issue, an inversion algorithm that jointly estimates geoacoustic properties and identifies mode number is proposed. It is successfully applied on a range-dependent track, and provides a reliable range-average estimation of geoacoustic properties of the mud layer, an important feature of the seabed on the experimental area.

Nonlinear time-warping made simple: A step-by-step tutorial on underwater acoustic modal separation with a single hydrophone

“…For in situ signals, source deconvolution requires a good measurement (or model) of the source signal. In a warping context, it has been successfully applied on lightbulb (Duan et al, 2016) and CSS data (Bonnel et al, 2019;Bonnel et al, 2018), with 2 ½0:01; 0:1.…”

“…The data and MATLAB code associated with these examples are provided as supplementary material. 1 Note that these examples are extracted from previous publications by the authors, and thus more detailed background information about the data and scenarios are available (Bonnel et al, 2014;Bonnel et al, 2018;Thode et al, 2017).…”

“…For our second example, we consider the sound from a Combustive Sound Source (CSS) (McNeese et al, 2010) recorded during the Seabed Characterization Experiment that took place on the New England mud patch in March/ April 2017 (Knobles and Wilson, 2017). The specific signal presented here has previously been studied in Bonnel et al (2018). Its range, known through GPS measurement, is 4.8 km.…”

“…While the first nine modes are modes 1 to 9 with little doubt, it is impossible to identify the last five high-order modes without further effort. The curious reader may read Bonnel et al (2018) to learn that the estimated high-order modes are modes 14 to 18. This example is a perfect illustration of warping's capability to filter modes, including highly dispersive high-order modes.…”

Vector Acoustic Analysis of Time-Separated Modal Arrivals From Explosive Sound Sources During the 2017 Seabed Characterization Experiment

“…The primary goal of the SBCEX is to study the acoustics of fine-grained muddy sediments that are a prominent feature of the experimental area. For example, the upper most sediment layer commencing at the water-sediment interface is known to consist of fine-grained mudlike material [1] with geoacoustic properties largely unknown before the SBCEX [2].…”