Inference of source signatures of merchant ships in shallow ocean environmentsa)

D P Knobles; Tracianne B Neilsen; William S Hodgkiss; John A Goff

doi:10.1121/10.0025983

Inference of source signatures of merchant ships in shallow ocean environmentsa)

J Acoust Soc Am. 2024 May 1;155(5):3144-3155. doi: 10.1121/10.0025983.

Authors

D P Knobles¹, Tracianne B Neilsen², William S Hodgkiss³, John A Goff⁴

Affiliations

¹ Knobles Scientific and Analysis, LLC, Austin, Texas 78731, USA.
² Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602, USA.
³ Scripps Institute of Oceanography, University of California at San Diego, La Jolla, California 92037, USA.
⁴ Institute for Geophysics, University of Texas at Austin, Austin, Texas 78758, USA.

PMID: 38727548
DOI: 10.1121/10.0025983

Abstract

An ocean acoustics experiment in 2017 near a shipping lane on the New England continental shelf in about 75 m of water provided an opportunity to evaluate a methodology to extract source signatures of merchant ships in a bottom-limited environment. The data of interest are the received acoustic levels during approximately 20 min time intervals centered at the closest position of approach (CPA) time for each channel on two 16-element vertical line arrays. At the CPA ranges, the received levels exhibit a frequency-dependent peak and null structure, which possesses information about the geophysical properties of the seabed, such as the porosity and sediment thickness, and the characterization of the source, such as an effective source depth. The modeled seabed is represented by two sediment layers, parameterized with the viscous grain shearing (VGS) model, which satisfies causality, over a fixed deep layered structure. Inferred estimates of the implicit source levels require averaging an error function over the full 20 min time intervals. Within the 200-700 Hz band, the Wales-Heitmeyer model captures the inferred frequency dependence of the source levels.