scholarly journals The Effects of Bubble Scattering on Sound Propagation in Shallow Water

2021 ◽  
Vol 9 (12) ◽  
pp. 1441
Author(s):  
Ruoyun Liu ◽  
Zhenglin Li
Keyword(s):  
Energy Loss ◽  
Shallow Water ◽  
Sound Propagation ◽  
Transmission Loss ◽  
Sound Field ◽  
Sea Surface ◽  
Statistical Characteristics ◽  
Strong Wind ◽  
Scattering Attenuation ◽  
Bubble Layer

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.

Influences Analysis of Environmental Parameters on Sound Propagation in Shallow Water

2014 ◽  
Vol 556-562 ◽  
pp. 4815-4819
Author(s):  
Shahabuddin Shaikh ◽  
Yi Wang Huang
Keyword(s):  
Shallow Water ◽  
Sound Speed ◽  
Sound Propagation ◽  
Transmission Loss ◽  
Water Environment ◽  
Environmental Parameters ◽  
Sea Surface ◽  
Water Medium ◽  
Sea Bottom ◽  
Shallow Water Environment

The objectives of this paper are to analyze the effectiveness of parameters on sound propagation in a shallow-water environment. The procedure for calculation of transmission loss is only the method to analyze the influence of environmental parameters. The normal mode approach is carried out for the calculation of transmission loss. And it is conducted in the range independent environment Transmission loss for sound propagation in shallow water depends upon many natural variables such as sea surface, water medium, and sea bottom. Analyses are finalized on the results obtained by considering two types of sound channels. The results indicated that acoustic transmission loss in a shallow-water environment is dependent on the source & receiver depths, sea surface, sound speed profile (SSP) in water, sound speed in bottom, density of water & bottom, propagation range and frequency. It is necessary to mention that better transmission was found during the sound velocity increases with depth; whereas the poor transmission occurred in negative gradient channel.

Comparison of Sound Propagation Characteristic between Deep and Shallow Water

2014 ◽  
Vol 577 ◽  
pp. 1198-1201
Author(s):  
Zhang Liang ◽  
Chun Xia Meng ◽  
Hai Tao Xiao
Keyword(s):  
Shallow Water ◽  
Deep Water ◽  
Sound Speed ◽  
Sound Propagation ◽  
Spherical Wave ◽  
Sound Field ◽  
Propagation Loss ◽  
Speed Profile ◽  
Sound Speed Profile ◽  
Propagation Law

The physical characteristics are compared between shallow and deep water, in physics and acoustics, respectively. There is a specific sound speed profile in deep water, which is different from which in shallow water, resulting in different sound propagation law between them. In this paper, the sound field distributions are simulated under respective typical sound speed profile. The color figures of sound intensity are obtained, in which the horizontal ordinate is distance, and the vertical ordinate is depth. Then we can get some important characteristics of sound propagation. The results show that the seabed boundary is an important influence on sound propagation in shallow water, and sound propagation loss in deep water convergent zone is visibly less than which in spherical wave spreading. We can realize the remote probing using the acoustic phenomenon.

scholarly journals Characteristics of Low-Frequency Acoustic Wave Propagation in Ice-Covered Shallow Water Environment

2021 ◽  
Vol 11 (17) ◽  
pp. 7815
Author(s):  
Shande Li ◽  
Shuai Yuan ◽  
Shaowei Liu ◽  
Jian Wen ◽  
Qibai Huang ◽  
...  
Keyword(s):  
Parabolic Equation ◽  
Target Detection ◽  
Acoustic Field ◽  
Sound Propagation ◽  
Transmission Loss ◽  
Low Frequency ◽  
Sound Field ◽  
The Arctic ◽  
Long Distance ◽  
Propagation Law

Mastering the sound propagation law of low-frequency signals in the Arctic is a major frontier basic research demand to improve the level of detection, communication, and navigation technology. It is of practical significance for long-distance sound propagation and underwater target detection in the Arctic Ocean. Therefore, how to establish an effective model to study the characteristics of the acoustic field in the Arctic area has always been a hot topic in polar acoustic research. Aimed at solving this problem, a mathematical polar acoustic field model with an elastic seafloor is developed based on a range-dependent elastic parabolic equation theory. Moreover, this method is applied to study the characteristics of polar sound propagation for the first attempt. The validity and effectiveness of the method and model are verified by the elastic normal mode method. Simultaneously, the propagation characteristics of low-frequency signals are studied in a polar sound field from three aspects, which are seafloor parameters, sea depth, and ice thickness. The results show that the elastic parabolic equation method can be well utilized to the Arctic low-frequency acoustic field. The analysis of the influence factors of the polar sound field reveals the laws of sound transmission loss of low-frequency signals, which is of great significance to provide information prediction for underwater submarine target detection and target recognition.

scholarly journals Effects of wind-generated bubbles layer on sound propagation underneath rough sea surface in shallow water

2020 ◽  
Vol 69 (2) ◽  
pp. 024303
Author(s):  
Mei-Juan Yao ◽  
Li-Cheng Lu ◽  
Bing-Wen Sun ◽  
Sheng-Ming Guo ◽  
Li Ma
Keyword(s):  
Shallow Water ◽  
Sound Propagation ◽  
Sea Surface ◽  
Rough Sea Surface ◽  
Rough Sea

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

2021 ◽  
Vol 9 (11) ◽  
pp. 1269
Author(s):  
Andrey Lunkov ◽  
Danila Sidorov ◽  
Valery Petnikov
Keyword(s):  
Shallow Water ◽  
Parabolic Equations ◽  
Acoustic Waves ◽  
Sound Propagation ◽  
Transmission Loss ◽  
Three Dimensional ◽  
Transitional Region ◽  
Wave Effect ◽  
Low Frequencies ◽  
Horizontal Refraction

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.

Sound Field Modeling with Bottom Reflective Parameters (P,Q) Based on Parabolic Equation

2020 ◽  
Vol 28 (04) ◽  
pp. 2050029
Author(s):  
C. J. Zhang ◽  
J. R. WU ◽  
Z. D. Zhao ◽  
L. Ma ◽  
E. C. Shang
Keyword(s):  
Sound Propagation ◽  
Transmission Loss ◽  
Low Frequency ◽  
Sound Field ◽  
Propagation Models ◽  
Acoustical Properties ◽  
Sea Bottom ◽  
Model Independent ◽  
The Mean ◽  
Parameter Coupling

Acoustical properties of the sea bottom can be described using geoacoustic (GA) models. Most existing propagation models use GA parameters as the bottom properties. It is difficult to obtain GA parameters for a layered bottom because of inter parameter coupling. These problems can be solved by inverting the model-independent reflective parameters P and Q. For a multilayered bottom, a sound field computation model, RamPQ, is developed using the mapping of GA and (P, Q) spaces. The mean square error of the transmission loss in numerical simulations and experimental data for low-frequency sound propagation are employed to validate RamPQ and demonstrate the performance of the model.

scholarly journals Sound Propagation with Undulating Bottom in Shallow Water

2021 ◽  
Vol 9 (9) ◽  
pp. 1010
Author(s):  
Dai Liu ◽  
Zhenglin Li ◽  
Guangxu Wang ◽  
Yunfeng Liu
Keyword(s):  
Shallow Water ◽  
Sound Propagation ◽  
Grazing Angle ◽  
Sound Field ◽  
Equation Model ◽  
Field Energy ◽  
Flat Bottom ◽  
Sea Bottom ◽  
The Difference ◽  
Energy Convergence

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.

scholarly journals A Green’s Function for Acoustic Problems in Pekeris Waveguide Using a Rigorous Image Source Method

2021 ◽  
Vol 11 (6) ◽  
pp. 2722
Author(s):  
Zhiwen Qian ◽  
Dejiang Shang ◽  
Yuan Hu ◽  
Xinyang Xu ◽  
Haihan Zhao ◽  
...  
Keyword(s):  
Green’S Function ◽  
Shallow Water ◽  
Green's Function ◽  
Plane Waves ◽  
Spherical Wave ◽  
Sound Field ◽  
Efficient Computation ◽  
Image Source ◽  
Source Method ◽  
Pekeris Waveguide

The Green’s function (GF) directly eases the efficient computation for acoustic radiation problems in shallow water with the use of the Helmholtz integral equation. The difficulty in solving the GF in shallow water lies in the need to consider the boundary effects. In this paper, a rigorous theoretical model of interactions between the spherical wave and the liquid boundary is established by Fourier transform. The accurate and adaptive GF for the acoustic problems in the Pekeris waveguide with lossy seabed is derived, which is based on the image source method (ISM) and wave acoustics. First, the spherical wave is decomposed into plane waves in different incident angles. Second, each plane wave is multiplied by the corresponding reflection coefficient to obtain the reflected sound field, and the field is superposed to obtain the reflected sound field of the spherical wave. Then, the sound field of all image sources and the physical source are summed to obtain the GF in the Pekeris waveguide. The results computed by this method are compared with the standard wavenumber integration method, which verifies the accuracy of the GF for the near- and far-field acoustic problems. The influence of seabed attenuation on modal interference patterns is analyzed.

scholarly journals Under-ice shallow-water sound propagation and communication in the Baltic Sea

2013 ◽  
Author(s):  
Erland Sangfelt ◽  
Sven Ivansson ◽  
Ilkka Karasalo
Keyword(s):  
Baltic Sea ◽  
Shallow Water ◽  
Sound Propagation ◽  
The Baltic Sea ◽  
The Baltic
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