Source Depth Estimation Using a Horizontal Array by Matched-Mode Processing in the Frequency-Wavenumber Domain

Barbara Nicolas,Jérôme I Mars,Jean-Louis Lacoume

doi:10.1155/asp/2006/65901

Barbara Nicolas, Jérôme I Mars + Show 1 more

Open Access

https://doi.org/10.1155/asp/2006/65901

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Abstract

In shallow water environments, matched-field processing (MFP) and matched-mode processing (MMP) are proven techniques for doing source localization. In these environments, the acoustic field propagates at long range as depth-dependent modes. Given a knowledge of the modes, it is possible to estimate source depth. In MMP, the pressure field is typically sampled over depth with a vertical line array (VLA) in order to extract the mode amplitudes. In this paper, we focus on horizontal line arrays (HLA) as they are generally more practical for at sea applications. Considering an impulsive low-frequency source (1-100 Hz) in a shallow water environment (100-400 m), we propose an efficient method to estimate source depth by modal decomposition of the pressure field recorded on an HLA of sensors. Mode amplitudes are estimated using the frequency-wavenumber transform, which is the 2D Fourier transform of a time-distance section. We first study the robustness of the presented method against noise and against environmental mismatches on simulated data. Then, the method is applied both to at sea and laboratory data. We also show that the source depth estimation is drastically improved by incorporating the sign of the mode amplitudes.

Highlights

Passive source localization in shallow water environments has been studied for many decades in underwater acoustics as many sources of interest are present in the ocean: marine mammals, fish, and submarines
As information extraction using a horizontal line array (HLA) is generally more adapted to practical applications, we propose a matched-mode method to estimate source depth using an HLA of sensors placed on the sea bottom
vertical line array (VLA) matched-mode methods cannot be used in this case, so we develop a new method to extract mode amplitudes

Summary

Introduction

Passive source localization in shallow water environments has been studied for many decades in underwater acoustics as many sources of interest are present in the ocean: marine mammals, fish, and submarines. These sources emit acoustic waves at different frequencies and localization methods must be adapted to these frequencies. The acoustic field received on an array of sensors is simulated This field is compared to the pressure field recorded on a real array, using an objective function, which is often defined as the correlation function between real and simulated pressure fields (Bartlett correlator). The main drawback of MFP methods is their sensitivity to environmental mismatch due to the use of the global acoustic field

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Discussion

Conclusion