TY - JOUR
T1 - A Direct Method for the Estimation of Sediment Sound Speed with a Horizontal Array in Shallow Water
AU - Lin, Tao
AU - Michalopoulou, Zoi Heleni
N1 - Funding Information:
This work was supported by the U.S. Office of Naval Research under Grants N000141010073 and N000141310077.
Publisher Copyright:
© 1976-2012 IEEE.
Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 2017/1
Y1 - 2017/1
N2 - In this paper, a fast approach for estimating sediment sound speed in a shallow-water environment is developed. Under certain assumptions, this algorithm recovers the seabed sound-speed profile using pressure field measurements at low frequencies. The geometry of the problem involves measuring the pressure at horizontally placed hydrophones in the water column. The Deift-Trubowitz integral equation is then solved. This work introduces two methods for this task. The first is a modified Born approximation that builds upon a standard first-order approximation; the second is based on interpolating the integrand. It is shown with synthetic data that these methods work well with successful sound-speed estimation and identification of sharp discontinuities in sound speed. Although the methods are stable and effective with noise-free data, problems arise when noise contaminates the acoustic field. Regularization approaches, reducing the disruptive effect of singular points and smoothing a measured reflection coefficient, are developed to remedy this problem, leading to improved results in noisy environments. In addition to providing sound-speed estimates, the method also computes sediment thickness. This feature is of particular interest, since it makes the method suitable as a preprocessing step providing useful information to other inversion methods. Sensitivity analyses demonstrate that some assumptions required for the approach implementation are not restrictive.
AB - In this paper, a fast approach for estimating sediment sound speed in a shallow-water environment is developed. Under certain assumptions, this algorithm recovers the seabed sound-speed profile using pressure field measurements at low frequencies. The geometry of the problem involves measuring the pressure at horizontally placed hydrophones in the water column. The Deift-Trubowitz integral equation is then solved. This work introduces two methods for this task. The first is a modified Born approximation that builds upon a standard first-order approximation; the second is based on interpolating the integrand. It is shown with synthetic data that these methods work well with successful sound-speed estimation and identification of sharp discontinuities in sound speed. Although the methods are stable and effective with noise-free data, problems arise when noise contaminates the acoustic field. Regularization approaches, reducing the disruptive effect of singular points and smoothing a measured reflection coefficient, are developed to remedy this problem, leading to improved results in noisy environments. In addition to providing sound-speed estimates, the method also computes sediment thickness. This feature is of particular interest, since it makes the method suitable as a preprocessing step providing useful information to other inversion methods. Sensitivity analyses demonstrate that some assumptions required for the approach implementation are not restrictive.
KW - Direct methods
KW - geoacoustic inversion
KW - sediment sound speed
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U2 - 10.1109/JOE.2016.2541925
DO - 10.1109/JOE.2016.2541925
M3 - Article
AN - SCOPUS:84966264778
SN - 0364-9059
VL - 42
SP - 208
EP - 218
JO - IEEE Journal of Oceanic Engineering
JF - IEEE Journal of Oceanic Engineering
IS - 1
M1 - 7464826
ER -