Journal of Marine Science and Engineering

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2 pages, 174 KiB

Open AccessEditorial

Modeling Techniques for Underwater Acoustic Scattering and Propagation (Including 3D Effects)

by Pavel Petrov, Boris Katsnelson and Zhenglin Li

J. Mar. Sci. Eng. 2022, 10(9), 1192; https://doi.org/10.3390/jmse10091192 - 26 Aug 2022

Cited by 3 | Viewed by 1432

Abstract

Almost three years have passed since the publication of the first Special Issue on three-dimensional underwater acoustics in 2019 [...] Full article

(This article belongs to the Special Issue Modeling Techniques for Underwater Acoustic Scattering and Propagation (including 3D Effects))

Research

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15 pages, 5219 KiB

Open AccessArticle

The Effects of Sound Speed Profile to the Convergence Zone in Deep Water

by Shuanglin Wu, Zhenglin Li, Jixing Qin, Mengyuan Wang and Wen Li

J. Mar. Sci. Eng. 2022, 10(3), 424; https://doi.org/10.3390/jmse10030424 - 15 Mar 2022

Cited by 8 | Viewed by 3729

Abstract

The structure of a sound speed profile (SSP) in deep water causes refraction of sound rays and Convergence Zones (CZs) of high intensity where the rays focus at shallow depth. Study of sound field characteristics in the CZs has always been the focus [...] Read more.

The structure of a sound speed profile (SSP) in deep water causes refraction of sound rays and Convergence Zones (CZs) of high intensity where the rays focus at shallow depth. Study of sound field characteristics in the CZs has always been the focus of deep-water acoustics research. Many studies have been conducted on sound propagation in different parts of the oceans with different environments and, in this paper, the range and width of CZ is analyzed in the East Indian Ocean (EIO) and the South China Sea (SCS). Through the experimental data collected in different seasons with the propagation conditions change in the EIO and the SCS, we observe that the SSPs in different marine environments have a significant impact on the CZs of deep water. The sound channel mixing layer and isothermal layer have great effect on the CZ ranges. The water depths in the two experimental areas are similar, the range of the first CZ in the EIO is 7–8 km farther than that in the SCS, and the width of the CZs in the EIO is about 2–3 km narrower than that in the SCS. The surface mixed layer and the thermocline affect the CZ width but has little effect on the CZ range when the sound speed at the source and the bottom are practically the same. As the propagation conditions change along the seasons in the EIO, the range of the first CZ is almost the same, but the width of the CZs in the summer is about 2 km narrower than that in the spring. The water depth affects the CZ width but has little effect on the CZ range if the CZs can be formed. The different CZ characteristics between EIO and SCS are explained by both theoretical calculation and numerical simulation. The influence of the SSP structure and water depth on the CZ range are analyzed and the corresponding mechanism is explained. The research results are of great significance for underwater acoustic detection in deep sea. Full article

(This article belongs to the Special Issue Modeling Techniques for Underwater Acoustic Scattering and Propagation (including 3D Effects))

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17 pages, 5774 KiB

Open AccessArticle

Sound Field Fluctuations in Shallow Water in the Presence of Moving Nonlinear Internal Waves

by Yanyu Jiang, Valery Grigorev and Boris Katsnelson

J. Mar. Sci. Eng. 2022, 10(1), 119; https://doi.org/10.3390/jmse10010119 - 17 Jan 2022

Cited by 9 | Viewed by 1636

Abstract

Fluctuations of sound intensity in the presence of moving nonlinear internal waves (NIWs) are studied. Prior works revealed the existence of peaks in the spectrum of these fluctuations due to mode coupling. In the given paper, the results of experiment ASIAEX 2001 are [...] Read more.

Fluctuations of sound intensity in the presence of moving nonlinear internal waves (NIWs) are studied. Prior works revealed the existence of peaks in the spectrum of these fluctuations due to mode coupling. In the given paper, the results of experiment ASIAEX 2001 are considered. Episodes are analyzed when soliton-like NIW move for ~6 h approximately along an acoustic track of length ~30 km. The depth of the ocean changes from ~350 m (position of the source) up to ~120 m near the receiver (Vertical Line Array). The source, placed near the bottom, transmitted pulses (M-sequences) with a frequency of 224 Hz. Theoretical analysis and numerical modeling show that peak frequencies in the spectrum of intensity fluctuations correspond to the most strongly interacting pairs of modes: in the given case pairs 2–3 and 3–4 and values of dominating frequencies are determined by the spatial scale of interference beating Λ of coupling modes and by the speed v of NIW. Due to the fact that in the narrowing channel velocity v decreases as well as the value of Λ, the predominant frequency as a function of time remains approximately the same. Results of modeling are in a good agreement with experimental data. Full article

(This article belongs to the Special Issue Modeling Techniques for Underwater Acoustic Scattering and Propagation (including 3D Effects))

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11 pages, 786 KiB

Open AccessArticle

Estimating Sound Exposure Levels Due to a Broadband Source over Large Areas of Shallow Sea

by Denis Manul’chev, Andrey Tyshchenko, Mikhail Fershalov and Pavel Petrov

J. Mar. Sci. Eng. 2022, 10(1), 82; https://doi.org/10.3390/jmse10010082 - 08 Jan 2022

Cited by 6 | Viewed by 1336

Abstract

3D sound propagation modeling in the context of acoustic noise monitoring problems is considered. A technique of effective source spectrum reconstruction from a reference single-hydrophone measurement is discussed, and the procedure of simulation of sound exposure level (SEL) distribution over a large sea [...] Read more.

3D sound propagation modeling in the context of acoustic noise monitoring problems is considered. A technique of effective source spectrum reconstruction from a reference single-hydrophone measurement is discussed, and the procedure of simulation of sound exposure level (SEL) distribution over a large sea area is described. The proposed technique is also used for the modeling of pulse signal waveforms at other receiver locations, and results of a direct comparison with the pulses observed in the experimental data is presented. Full article

(This article belongs to the Special Issue Modeling Techniques for Underwater Acoustic Scattering and Propagation (including 3D Effects))

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10 pages, 3355 KiB

Open AccessArticle

A Study on the Estimation of Source Bearing in an ASA Wedge: Diminishing the Estimation Error Caused by Horizontal Refraction

by Jianbo Zhou, Jun Tang and Yixin Yang

J. Mar. Sci. Eng. 2021, 9(12), 1449; https://doi.org/10.3390/jmse9121449 - 18 Dec 2021

Cited by 3 | Viewed by 1874

Abstract

The performance of warping transformation in diminishing the error in underwater source-bearing estimation, caused by horizontal refraction effects (also named 3D effects), is studied. First, the capability of warping transformation for separating the normal modes, as well as their direct and horizontally refracted [...] Read more.

The performance of warping transformation in diminishing the error in underwater source-bearing estimation, caused by horizontal refraction effects (also named 3D effects), is studied. First, the capability of warping transformation for separating the normal modes, as well as their direct and horizontally refracted paths, in a standard Acoustical Society of America (ASA) wedge is demonstrated. Second, the error values for source bearing estimation in three different manners, i.e., using the full signal, using its component corresponding to the first mode, and using the component of the latter corresponding only to the direct path are compared for the same wedge case. The results show that the estimation error can be significantly reduced by beamforming, with only the first mode, or using the direct path of the first mode in cases where there exists a horizontally refracted path of the first mode. Full article

(This article belongs to the Special Issue Modeling Techniques for Underwater Acoustic Scattering and Propagation (including 3D Effects))

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20 pages, 6340 KiB

Open AccessArticle

The Effects of Bubble Scattering on Sound Propagation in Shallow Water

by Ruoyun Liu and Zhenglin Li

J. Mar. Sci. Eng. 2021, 9(12), 1441; https://doi.org/10.3390/jmse9121441 - 16 Dec 2021

Cited by 6 | Viewed by 3003

Abstract

As sea waves break, a bubble layer forms beneath the sea surface. The bubble scattering affects sound propagation, thus influencing the accuracy of sound field prediction. This paper aims to investigate the effects of bubble scattering on the statistical characteristics of the sound [...] Read more.

As sea waves break, a bubble layer forms beneath the sea surface. The bubble scattering affects sound propagation, thus influencing the accuracy of sound field prediction. This paper aims to investigate the effects of bubble scattering on the statistical characteristics of the sound field, the distribution of transmission loss (TL), and the average scattering attenuation in shallow water. A bubble layer model based on the bubble spectrum and a parallel Parabolic Equation (PE) model are combined to calculate and analyse the sound field in the marine environment with bubbles. The effects of the bubble layer are then compared with those of the fluctuant sea surface. The results show that the bubble scattering causes additional energy loss and random fluctuations of the sound field. The TL distribution properties and the average scattering attenuation are related to the wind speed, range, frequency, and source position relative to the negative gradient sound speed layer in shallow water. The comparison demonstrates that the random variation caused by the fluctuation of the sea surface is more significant than that caused by bubbles, and the energy loss caused by bubble scattering is more significant than the fluctuant sea surface under strong wind conditions. Full article

(This article belongs to the Special Issue Modeling Techniques for Underwater Acoustic Scattering and Propagation (including 3D Effects))

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27 pages, 8885 KiB

Open AccessArticle

Geoacoustic Estimation of the Seafloor Sound Speed Profile in Deep Passive Margin Setting Using Standard Multichannel Seismic Data

by Ernst Uzhansky, Omri Gadol, Guy Lang, Boris Katsnelson, Shelly Copel, Tom Kazaz and Yizhaq Makovsky

J. Mar. Sci. Eng. 2021, 9(12), 1423; https://doi.org/10.3390/jmse9121423 - 13 Dec 2021

Cited by 4 | Viewed by 3263

Abstract

Seafloor geoacoustic properties are important in determining sound propagation in the marine environment, which broadly affects sub-sea activities. However, geoacoustic investigation of the deep seafloor, which is required by the recent expansion of deep-water operations, is challenging. This paper presents a methodology for [...] Read more.

Seafloor geoacoustic properties are important in determining sound propagation in the marine environment, which broadly affects sub-sea activities. However, geoacoustic investigation of the deep seafloor, which is required by the recent expansion of deep-water operations, is challenging. This paper presents a methodology for estimating the seafloor sound speed,

c_{0}

, and a sub-bottom velocity gradient,

K

, in a relatively deep-water-compacting (~1000 m) passive-margin setting, based on standard commercial 2D seismic data. Here we study the seafloor of the southeastern Mediterranean margin based on data from three commercial seismic profiles, which were acquired using a 7.2 km-long horizontal receiver array. The estimation applies a geoacoustic inversion of the wide-angle reflections and the travel times of the head waves of bending rays. Under the assumption of a constant positive

K

, the geoacoustic inversion converges to a unique set of parameters that best satisfy the data. The analysis of 24 measurement locations revealed an increase in the average estimates of

c_{0}

from 1537

\pm

13 m s⁻¹ to 1613

\pm

12 m s⁻¹ for seafloor depths between ~1150 m and ~1350 m.

K

ranged between 0.75 and 0.85 m s⁻¹ with an average of 0.80

\pm

0.035 s⁻¹. The parameters were consistent across the different locations and seismic lines and they match the values that were obtained through depth-migration-velocity analysis and empiric relations, thereby validating our estimation methodology. Full article

(This article belongs to the Special Issue Modeling Techniques for Underwater Acoustic Scattering and Propagation (including 3D Effects))

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10 pages, 3154 KiB

Open AccessFeature PaperArticle

Horizontal Refraction of Acoustic Waves in Shallow-Water Waveguides Due to an Inhomogeneous Bottom Structure

by Andrey Lunkov, Danila Sidorov and Valery Petnikov

J. Mar. Sci. Eng. 2021, 9(11), 1269; https://doi.org/10.3390/jmse9111269 - 15 Nov 2021

Cited by 9 | Viewed by 1704

Abstract

Three-Dimensional (3-D) sound propagation in a shallow-water waveguide with a constant depth and inhomogeneous bottom is studied through numerical simulations. As a model of inhomogeneity, a transitional region between an acoustically soft and hard bottom is considered. Depth-averaged transmission loss simulations using the [...] Read more.

Three-Dimensional (3-D) sound propagation in a shallow-water waveguide with a constant depth and inhomogeneous bottom is studied through numerical simulations. As a model of inhomogeneity, a transitional region between an acoustically soft and hard bottom is considered. Depth-averaged transmission loss simulations using the “horizontal rays and vertical modes” approach and mode parabolic equations demonstrate the horizontal refraction of sound in this region, even if the water column is considered homogeneous. The observed wave effect is prominent at low frequencies, at which the water depth does not exceed a few acoustic wavelengths. The obtained results within the simplified model are verified by the simulations for a real seabed structure in the Kara Sea. Full article

(This article belongs to the Special Issue Modeling Techniques for Underwater Acoustic Scattering and Propagation (including 3D Effects))

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16 pages, 4146 KiB

Open AccessArticle

Joint Tracking of Source and Environment Using Improved Particle Filtering in Shallow Water

by Miao Dai, Yaan Li, Jinying Ye and Kunde Yang

J. Mar. Sci. Eng. 2021, 9(11), 1203; https://doi.org/10.3390/jmse9111203 - 31 Oct 2021

Cited by 2 | Viewed by 1440

Abstract

Shallow water is a complex sound propagation medium, which is affected by the varying spatial–temporal ocean environment. Taking this complexity into account, the classical processing techniques of source localization and environmental inversion may be improved. In this work, a joint tracking approach for [...] Read more.

Shallow water is a complex sound propagation medium, which is affected by the varying spatial–temporal ocean environment. Taking this complexity into account, the classical processing techniques of source localization and environmental inversion may be improved. In this work, a joint tracking approach for the moving source and environmental parameters of the range-dependent and time-evolving environment in shallow water is presented. The tracking scheme treats both the source parameters (e.g., source depth, range, and speed) and the environmental parameters (e.g., water column sound speed profile (SSP) and sediment parameters) at the source location as unknown variables that evolve as the source moves. To counter sample impoverishment and robustly characterize the evolution of the parameters, an improved particle filter (PF), which is an extension of the standard PF, is proposed. Two examples with simulated data in a slowly changing environment and experimental data collected during the ASIAEX experiment are utilized to demonstrate the effectiveness of the joint approach. The results show that we were able to track the source and environmental parameters simultaneously, and the uncertainties were evaluated in the form of time-evolving posterior probability densities (PPDs). The performance comparison confirms that the improved PF is superior to the standard PF, as it can reduce the parameter uncertainties. The tracking capabilities of the improved PF were verified with high accuracy in real-time source localization and well-estimated rapidly varying parameters. Moreover, the influence of different particle numbers on the improved PF tracking performance is also illustrated. Full article

(This article belongs to the Special Issue Modeling Techniques for Underwater Acoustic Scattering and Propagation (including 3D Effects))

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15 pages, 9700 KiB

Open AccessArticle

Three-Dimensional Sound Propagation in the South China Sea with the Presence of Seamount

by Shenghao Li, Zhenglin Li, Wen Li and Yanxin Yu

J. Mar. Sci. Eng. 2021, 9(10), 1078; https://doi.org/10.3390/jmse9101078 - 01 Oct 2021

Cited by 3 | Viewed by 1677

Abstract

Seamounts have important effects on sound propagation in deep water. A sound propagation experiment was conducted in the South China Sea in 2016. The three-dimensional (3D) effects of a seamount on sound propagation are observed in different propagation tracks. Ray methods (BELLHOP N×2D [...] Read more.

Seamounts have important effects on sound propagation in deep water. A sound propagation experiment was conducted in the South China Sea in 2016. The three-dimensional (3D) effects of a seamount on sound propagation are observed in different propagation tracks. Ray methods (BELLHOP N×2D and 3D models) are used to analyze and explain the phenomena. The results show that 3D effects have obvious impacts on a sound field within a horizontal refraction zone behind the seamount because some sound beams cannot reach the receiver for the horizontal refraction effects, which impacts the sound field within a certain angle range behind the seamount. The arrival structure results show that the eigenrays after horizontal reflection will arrive at the receiver earlier than those obtained from the two-dimensional (2D) model within the horizontal refraction zone behind the seamount. This means that the horizontal reflection effect of a seamount will cause the shortening of sound propagation paths. Finally, in the reflection zone in front of the seamount, the 2D and 3D TL results show that the shape of the reflection zone is similar to an “arch” type, and the horizontal refraction of sound waves has little effect on the TLs in the reflection zone of a seamount. Full article

(This article belongs to the Special Issue Modeling Techniques for Underwater Acoustic Scattering and Propagation (including 3D Effects))

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8 pages, 381 KiB

Open AccessArticle

Generalized Form of the Invariant Imbedding Method and Its Application to the Study of Back-Scattering in Shallow-Water Acoustics

by Mikhail Kazak, Konstantin Koshel and Pavel Petrov

J. Mar. Sci. Eng. 2021, 9(9), 1033; https://doi.org/10.3390/jmse9091033 - 19 Sep 2021

Cited by 5 | Viewed by 1586

Abstract

A generalized form of the matrix-invariant imbedding method was developed to solve boundary-value problems for coupled systems of Helmholtz-type equations. Within this approach, a boundary-value problem solution can be obtained by solving evolutionary first-order imbedding equations for a matrix-valued function. The proposed method [...] Read more.

A generalized form of the matrix-invariant imbedding method was developed to solve boundary-value problems for coupled systems of Helmholtz-type equations. Within this approach, a boundary-value problem solution can be obtained by solving evolutionary first-order imbedding equations for a matrix-valued function. The proposed method is applied to the solution of coupled equations for mode amplitudes describing the propagation of acoustic waves in a range-dependent shallow-water waveguide. The back-scattering of modes by bathymetry features is investigated, and the coefficients of the modal expansion of the wave reflected by an inhomogeneity in the bottom relief are computed. It is demonstrated that back-scattering is strongly connected with the modal interactions and that the back-scattered field consists of modes with numbers different from the number of the incident mode. Full article

(This article belongs to the Special Issue Modeling Techniques for Underwater Acoustic Scattering and Propagation (including 3D Effects))

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16 pages, 3555 KiB

Open AccessArticle

Sound Propagation with Undulating Bottom in Shallow Water

by Dai Liu, Zhenglin Li, Guangxu Wang and Yunfeng Liu

J. Mar. Sci. Eng. 2021, 9(9), 1010; https://doi.org/10.3390/jmse9091010 - 15 Sep 2021

Cited by 5 | Viewed by 2606

Abstract

An undulating bottom in shallow water has a significant effect on sound propagation. An acoustic propagation experiment was carried out in the East China Sea in 2020. Measurements along two separate propagation tracks with flat and undulating bottoms were obtained. Abnormal transmission losses [...] Read more.

An undulating bottom in shallow water has a significant effect on sound propagation. An acoustic propagation experiment was carried out in the East China Sea in 2020. Measurements along two separate propagation tracks with flat and undulating bottoms were obtained. Abnormal transmission losses (TLs) were observed along the track with the undulating bottom. By using the parabolic equation model RAM and ray theory, these abnormal TLs and the distribution of the sound field energy were analyzed. Numerical simulations indicate that under the shallow water condition with a negative thermocline and for a high frequency (1000 Hz), the incidence and reflection angles of sound rays on the sea bottom are changed due to the undulating sea bottom. The larger the inclination angle of the undulating bottom, the greater the grazing angle changes. These angles changes lead to different sound propagation paths for the undulating bottom and the flat bottom, resulting in the difference of TLs at a certain distance and depth. The undulating bottom will cause energy convergence in the mixed layer when the source and receiver locate above the thermocline. Full article

(This article belongs to the Special Issue Modeling Techniques for Underwater Acoustic Scattering and Propagation (including 3D Effects))

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21 pages, 4315 KiB

Open AccessArticle

A Finite Element Model for Underwater Sound Propagation in 2-D Environment

by Yi-Qing Zhou and Wen-Yu Luo

J. Mar. Sci. Eng. 2021, 9(9), 956; https://doi.org/10.3390/jmse9090956 - 03 Sep 2021

Cited by 3 | Viewed by 2174

Abstract

The finite element method is a popular numerical method in engineering applications. However, there is not enough research about the finite element method in underwater sound propagation. The finite element method can achieve high accuracy and great universality. We aim to develop a [...] Read more.

The finite element method is a popular numerical method in engineering applications. However, there is not enough research about the finite element method in underwater sound propagation. The finite element method can achieve high accuracy and great universality. We aim to develop a three-dimensional finite element model focusing on underwater sound propagation. As the foundation of this research, we put forward a finite element model in the Cartesian coordinate system for a sound field in a two-dimensional environment. We firstly introduce the details of the implementation of the finite element model, as well as different methods to deal with boundary conditions and a comparison of these methods. Then, we use four-node quadrilateral elements to discretize the physical domain, and apply the perfectly matched layer approach to deal with the infinite region. After that, we apply the model to underwater sound propagation problems including the wedge-shaped waveguide benchmark problem and the problem where the bathymetry consists of a sloping region and a flat region. The results by the presented finite element model are in excellent agreement with analytical and benchmark numerical solutions, implying that the presented finite element model is able to solve complex two-dimensional underwater sound propagation problems accurately. In the end, we compare the finite element model with the popular normal mode model KRAKEN by calculating sound fields in Pekeris waveguides, and find that the finite element model has better universality than KRAKEN. Full article

(This article belongs to the Special Issue Modeling Techniques for Underwater Acoustic Scattering and Propagation (including 3D Effects))

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13 pages, 1188 KiB

Open AccessEditor’s ChoiceArticle

Improving the Performance of Mode-Based Sound Propagation Models by Using Perturbation Formulae for Eigenvalues and Eigenfunctions

by Alena Zakharenko, Mikhail Trofimov and Pavel Petrov

J. Mar. Sci. Eng. 2021, 9(9), 934; https://doi.org/10.3390/jmse9090934 - 28 Aug 2021

Cited by 4 | Viewed by 1886

Abstract

Numerous sound propagation models in underwater acoustics are based on the representation of a sound field in the form of a decomposition over normal modes. In the framework of such models, the calculation of the field in a range-dependent waveguide (as well as [...] Read more.

Numerous sound propagation models in underwater acoustics are based on the representation of a sound field in the form of a decomposition over normal modes. In the framework of such models, the calculation of the field in a range-dependent waveguide (as well as in the case of 3D problems) requires the computation of normal modes for every point within the area of interest (that is, for each pair of horizontal coordinates x,y). This procedure is often responsible for the lion’s share of total computational cost of the field simulation. In this study, we present formulae for perturbation of eigenvalues and eigenfunctions of normal modes under the water depth variations in a shallow-water waveguide. These formulae can reduce the total number of mode computation instances required for a field calculation by a factor of 5–10. We also discuss how these formulae can be used in a combination with a wide-angle mode parabolic equation. The accuracy of such combined model is validated in a series of numerical examples. Full article

(This article belongs to the Special Issue Modeling Techniques for Underwater Acoustic Scattering and Propagation (including 3D Effects))

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