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.

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.

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 Statistical Patterns of Transmission Losses of Low-Frequency Sound in Shallow Sea Waveguides with Gaussian and Non-Gaussian Fluctuations

2019 ◽  
Vol 9 (9) ◽  
pp. 1841
Author(s):  
Fengqin Zhu ◽  
Oleg E. Gulin ◽  
Igor O. Yaroshchuk
Keyword(s):  
Acoustic Field ◽  
Speed Of Sound ◽  
Transmission Loss ◽  
Low Frequency ◽  
Local Mode ◽  
Average Intensity ◽  
Slowing Down ◽  
Gaussian Fluctuations ◽  
Mode Method ◽  
Non Gaussian

Based on the local mode method, the problem of the average intensity (transmission loss) behavior in shallow waveguides with losses in the bottom and fluctuations of the speed of sound in water is considered. It was previously shown that the presence in a waveguide with absorbing penetrable bottom of 2D random inhomogeneities of the speed of sound leads to the appearance of strong fluctuations in the acoustic field already at relatively small distances from the sound source. One of the most important and interesting manifestations of this is the slowing down of the average intensity of the acoustic field compared with a waveguide, which has no such random inhomogeneities of the speed of sound. This paper presents the results of a numerical analysis of the decay of the average field intensity in the presence of both Gaussian and non-Gaussian fluctuations in the speed of sound. It is shown that non-Gaussian fluctuations do not fundamentally change the conclusion about reducing losses during the propagation of a sound signal but can enhance this effect.

Three-dimensional parabolic equation model for low frequency sound propagation in irregular urban canyons

2015 ◽  
Vol 137 (1) ◽  
pp. 310-320 ◽  
Author(s):  
Jean-Baptiste Doc ◽  
Bertrand Lihoreau ◽  
Simon Félix ◽  
Cédric Faure ◽  
Guillaume Dubois
Keyword(s):  
Parabolic Equation ◽  
Sound Propagation ◽  
Three Dimensional ◽  
Low Frequency ◽  
Equation Model ◽  
Frequency Sound

scholarly journals Infrasound propagation in the Arctic

2021 ◽  
Author(s):  
D. Wilson ◽  
Vladimir Ostashev ◽  
Michael Shaw ◽  
Michael Muhlestein ◽  
John Weatherly ◽  
...  
Keyword(s):  
Sound Propagation ◽  
Ground Surface ◽  
Polar Vortex ◽  
Basic Research ◽  
Arctic Region ◽  
Initial Step ◽  
The Arctic ◽  
Equation Modeling ◽  
Katabatic Wind ◽  
Long Distance

This report summarizes results of the basic research project “Infrasound Propagation in the Arctic.” The scientific objective of this project was to provide a baseline understanding of the characteristic horizontal propagation distances, frequency dependencies, and conditions leading to enhanced propagation of infrasound in the Arctic region. The approach emphasized theory and numerical modeling as an initial step toward improving understanding of the basic phenomenology, and thus lay the foundation for productive experiments in the future. The modeling approach combined mesoscale numerical weather forecasts from the Polar Weather Research and Forecasting model with advanced acoustic propagation calculations. The project produced significant advances with regard to parabolic equation modeling of sound propagation in a windy atmosphere. For the polar low, interesting interactions with the stratosphere were found, which could possibly be used to provide early warning of strong stratospheric warming events (i.e., the polar vortex). The katabatic wind resulted in a very strong low-level duct, which, when combined with a highly reflective icy ground surface, leads to efficient long-distance propagation. This information is useful in devising strategies for positioning sensors to monitor environmental phenomena and human activities.

scholarly journals Average Intensity of Low-Frequency Sound and Its Fluctuations in a Shallow Sea with a Range-Dependent Random Impedance of the Liquid Bottom

2021 ◽  
Vol 11 (23) ◽  
pp. 11575
Author(s):  
Fengqin Zhu ◽  
Oleg E. Gulin ◽  
Igor O. Yaroshchuk
Keyword(s):  
Speed Of Sound ◽  
Sound Propagation ◽  
Gaussian Function ◽  
Low Frequency ◽  
Sound Field ◽  
Water Layer ◽  
Correlation Radius ◽  
Model Parameters ◽  
Average Intensity ◽  
Frequency Sound

In this study, the problem of the influence of a horizontally inhomogeneous liquid bottom impedance, given by random Gaussian function of the speed of sound and by density, on the propagation of low-frequency sound in a shallow-water waveguide is considered. The model parameters are referenced to the conditions of sound propagation in the regions of the seas of the Russian Arctic shelf. By the example of statistical modeling of the sound field intensity, we show that sound speed fluctuations in the bottom lead to similar effects that were previously established for volumetric fluctuations of the speed of sound in the water layer. With the distance from the source, the decrease in the average intensity slows down in comparison with a deterministic medium in which there are no fluctuations. This deceleration of the decay of the intensity in a random waveguide can be significant already at short distances. Changes in the law of decay of intensity at a fixed frequency are mainly determined by the correlation radius of inhomogeneities and the average penetrability of the bottom, which leads to attenuation of sound propagating in the waveguide.

scholarly journals Theoretical Model of Acoustic Wave Propagation in Shallow Water

2017 ◽  
Vol 24 (2) ◽  
pp. 48-55 ◽  
Author(s):  
Eugeniusz Kozaczka ◽  
Grażyna Grelowska
Keyword(s):  
Shallow Water ◽  
Acoustic Field ◽  
Acoustic Waves ◽  
Sound Propagation ◽  
Low Frequency ◽  
Water Layer ◽  
Surface Shape ◽  
Shallow Sea ◽  
Multiple Reflections ◽  
Indirect Determination

Abstract The work is devoted to the propagation of low frequency waves in a shallow sea. As a source of acoustic waves, underwater disturbances generated by ships were adopted. A specific feature of the propagation of acoustic waves in shallow water is the proximity of boundaries of the limiting media characterised by different impedance properties, which affects the acoustic field coming from a source situated in the water layer “deformed” by different phenomena. The acoustic field distribution in the real shallow sea is affected not only by multiple reflections, but also by stochastic changes in the free surface shape, and statistical changes in the seabed shape and impedance. The paper discusses fundamental problems of modal sound propagation in the water layer over different types of bottom sediments. The basic task in this case was to determine the acoustic pressure level as a function of distance and depth. The results of the conducted investigation can be useful in indirect determination of the type of bottom.

Laboratory and in situ sound absorption measurement under a synthetized diffuse acoustic field

2019 ◽  
Vol 26 (4) ◽  
pp. 223-242
Author(s):  
Olivier Robin ◽  
Alain Berry ◽  
Celse Kafui Amédin ◽  
Noureddine Atalla ◽  
Olivier Doutres ◽  
...  
Keyword(s):  
Acoustic Field ◽  
Sound Absorption ◽  
Low Frequency ◽  
Sound Field ◽  
Geometrical Parameters ◽  
In Situ Conditions ◽  
Field Excitation ◽  
Acoustic Environments ◽  
Field Sound

This article reports numerical and experimental results concerning the estimation of the diffuse field sound absorption coefficient of several different materials under a synthetized diffuse acoustic field excitation in laboratory and in situ conditions. The proposed measurement method is based on a sound field reproduction approach and a synthetic array of acoustic monopoles facing the material to be tested. Numerical simulations are first conducted to optimize the geometrical parameters of the method and to compute theoretical sound absorption coefficients of the considered materials. Measurements on a set of six typical acoustic materials are then conducted following the standardized reverberant room method as well as the proposed approach in a hemi-anechoic room and in two realistic rooms. Albeit showing limitations in the low-frequency domain, the proposed method enables a significant reduction of the tested specimen dimensions compared with the reverberant room method and allows performing tests in non-ideal acoustic environments.

Transmission of Sound through Tied Walls: An Experimental Study

1998 ◽  
Vol 5 (2) ◽  
pp. 91-101
Author(s):  
Gülin Birlik
Keyword(s):  
Experimental Study ◽  
Experimental Work ◽  
High Frequency ◽  
Transmission Loss ◽  
Low Frequency ◽  
Sound Transmission ◽  
Sound Field ◽  
Continuous Reinforcement ◽  
Cavity Depth ◽  
Sound Transmission Class

Experimental work on the prediction of sound transmission loss, TL, of brick cavity walls, plastered on both faces, is presented. First double brick walls having either 2 cm or 5 cm cavity widths were subjected to a diffuse sound field. Then tied walls were tested. In order to assess the effect of the wall ties on TL values, two types of ties, namely unit and continuous reinforcement, were investigated. The low frequency TL of the walls was observed to be highly affected by the presence of ties. High frequency TL values were not strongly influenced by the ties. When the leaves of the double brick walls having 5 cm cavity depth were tied, regardless of the type of tie used, their Sound Transmission Class was decreased by 5 points.

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