Calculation of temporal, angular, and intensity characteristics of the sound field in a coastal area with an arbitrary bottom relief and a constant sound speed in the medium

2000 ◽  
Vol 46 (3) ◽  
pp. 302-309
Author(s):  
N. N. Komissarova
Keyword(s):  
Coastal Area ◽  
Sound Speed ◽  
Sound Field ◽  
Bottom Relief

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 An Acoustic Tomography Technique for Concurrently Observing the Structure of the Atmosphere and Water Bodies

2017 ◽  
Vol 34 (3) ◽  
pp. 617-629 ◽  
Author(s):  
Anthony Finn ◽  
Kevin Rogers
Keyword(s):  
Theoretical Analysis ◽  
Sound Speed ◽  
Water Surface ◽  
Low Frequency ◽  
Sound Field ◽  
Acoustic Signals ◽  
Acoustic Tomography ◽  
Radio Waves ◽  
Surface Errors ◽  
Underwater Sensors

AbstractThe opacity of water to radio waves means there are few, if any, techniques for remotely sensing it and the atmosphere concurrently. However, both these media are transparent to low-frequency sound (<300 Hz), which makes it possible to contemplate systems that take advantage of the natural integration along acoustic paths of signals propagating through both media. This paper proposes—and examines with theoretical analysis—a method that exploits the harmonics generated by the natural signature of a propeller-driven aircraft as it overflies an array of surface and underwater sensors. Correspondence of the projected and observed narrowband acoustic signals, which are monitored synchronously on board the aircraft and by both sensor sets, allows the exact travel time of detected rays to be related to a linear model of the constituent terms of sound speed. These observations may then be inverted using tomography to determine the inhomogeneous structures of both regions. As the signature of the aircraft comprises a series of harmonics between 50 Hz and 1 kHz, the horizontal detection limits of such a system may be up to a few hundred meters, depending on the depth of the sensors, roughness of the water surface, errors due to refraction, and magnitude of the sound field generated by the source aircraft. The approach would permit temperature, wind, and current velocity profiles to be observed both above and below the water’s surface.

scholarly journals Development and correctness analysis of the mathematical model of transport and suspension sedimentation depending on bottom relief variation

2018 ◽  
Vol 18 (4) ◽  
pp. 350-361
Author(s):  
A. I. Sukhinov ◽  
V. V. Sidoryakina
Keyword(s):  
Boundary Value Problem ◽  
Coastal Area ◽  
Boundary Value ◽  
Initial Boundary ◽  
Initial Boundary Value Problem ◽  
Quadratic Functional ◽  
Bottom Relief ◽  
Aquatic Medium ◽  
Initial Boundary Value ◽  
The Right

Introduction. The paper is devoted to the study on the three-dimensional model of transport and suspension sedimentation in the coastal area due to changes in the bottom relief. The model considers the following processes: advective transfer caused by the aquatic medium motion, micro-turbulent diffusion, and gravity sedimentation of suspended particles, as well as the bottom geometry variation caused by the particle settling or bottom sediment rising. The work objective was to conduct an analytical study of the correctness of the initial-boundary value problem corresponding to the constructed model.Materials and Methods. The change in the bottom relief aids in solution to the initial-boundary value problem for a parabolic equation with the lowest derivatives in a domain whose geometry depends on the desired function of the solution, which in general leads to a nonlinear formulation of the problem. The model is linearized on the time grid due to the “freezing” of the bottom relief within a single step in time and the subsequent recalculation of the bottom surface function on the basis of the changed function of the suspension concentration, as well as a possible change in the velocity vector of the aquatic medium.Research Results. For the linearized problem, a quadratic functional is constructed, and the uniqueness of the solution to the corresponding initial boundary value problem is proved within the limits of an unspecified time step. On the basis of the quadratic functional transformation, we obtain a prior estimate of the solution norm in the functional space L2 as a function of the integral time estimates of the right side, and the initial condition. Thus, the stability of the solution to the initial problem from the change of the initial and boundary conditions, the right-hand side function, is established.Discussion and Conclusions. The model can be of value for predicting the spread of contaminants and changes in the bottom topography, both under an anthropogenic impact and due to the natural processes in the coastal area.

scholarly journals Estimating the parameters of the seabed using the spatial characteristics of ocean ambient noise

2019 ◽  
Vol 283 ◽  
pp. 08004
Author(s):  
He Li ◽  
Xiniyi Guo ◽  
Li Ma ◽  
Guoli Song
Keyword(s):  
Experimental Data ◽  
Sound Speed ◽  
Critical Angle ◽  
Ambient Noise ◽  
Array Processing ◽  
Sound Field ◽  
Spatial Characteristics ◽  
Matched Field Processing ◽  
Spectrum Density ◽  
Snell Law

When solving traditional underwater problems, the boundary condition is always used to calculate the sound field. In practice, however, it is hard to get the boundary conditions of the seabed. So geoacoustics inversion is needed to acquire the parameters of the seabed. In this paper, a method estimating seabed parameters by using the spatial characteristics of ocean ambient noise is demonstrated without using matched-field processing. For the reason of the limit of the resolution of conventional beamforming (CBF), a method of synthetic array processing (SAP) is used because of some characters of cross-spectrum density matrix (CSDM). The result shows that the method of synthetic array processing enhanced the resolution of critical angle to some degree. By comparing the true bottomloss calculated by OASR, the result of traditional beamforming and the synthetic array processing, the result of synthetic array processing is closer to the true bottomloss than the result of traditional beamforming. After ensuring a range of critical angle, the sound speed of the seabed can be estimated by using Snell law. And then, an experimental data collected in Qingdao, China, 2016 is used to prove the validity of the method of synthetic array processing and estimate the local seabed parameters.

SOUND FIELD IN A WATER LAYER OF CHANGEABLE DEPTH EXCITED BY A SOURCE MOVING IN AIR

1995 ◽  
Vol 03 (03) ◽  
pp. 219-228
Author(s):  
VLADIMIR BULDYREV ◽  
NATALIE GRIGORIEVA
Keyword(s):  
Sound Speed ◽  
Finite Interval ◽  
Sound Field ◽  
Water Layer ◽  
Observation Point ◽  
Slow Time ◽  
Normal Waves ◽  
Sturm Liouville ◽  
The Subject ◽  
Shaped Domain

The subject of this paper is the construction of the nonstationary normal waves excited in the ocean of changeable depth by a source moving in the atmosphere. In the atmosphere, the sound speed is assumed to be constant and in water it depends on depth, slow horizontal coordinates as well as slow time. The bottom is assumed to be rigid. The source is radiating a signal with varying amplitude and phase. It is moving with a speed which is smaller than the sound speed in liquid. To find the nonstationary normal waves, the nonstationary variant of the well-known method of horizontal rays/vertical modes is used. Arising Sturm–Liouville problems in the semi-infinite interval are reduced to the Sturm–Liouville problems in the finite interval. The reduction allows one to avoid the regularization of improper integrals involving the eigenfunctions of the considered Sturm–Liouville problems. The variation of diverse characteristics of the normal waves in time is also investigated. It is shown that in a wedge–shaped domain, the nonstationary normal waves excited by the moving point source will be registered at the observation point before the source passes over it.

ENHANCED RAY THEORY

2001 ◽  
Vol 09 (01) ◽  
pp. 169-182 ◽  
Author(s):  
NICK MALTSEV
Keyword(s):  
Sound Speed ◽  
Sound Field ◽  
New Method ◽  
Analytic Approximation ◽  
Theory Approach ◽  
Field Calculation ◽  
Ray Theory ◽  
Method Of Calculation

The numerical problems of SWAM'99 workshop are quite challenging for any method of sound field calculation. This report presents a detailed description of the enhanced ray theory approach briefly outlined in Ref. 2. It contains a new method of phase and amplitude computation along the ray, a new method of calculation of eigenrays, and a new method of analytic approximation of sound-speed and density. An application of these methods is presented.

Decay of Temporary Threshold Shift in Noise

1973 ◽  
Vol 16 (2) ◽  
pp. 267-270 ◽  
Author(s):  
John H. Mills ◽  
Seija A. Talo ◽  
Gloria S. Gordon
Keyword(s):  
Sound Field ◽  
Threshold Shift ◽  
Temporary Threshold Shift ◽  
Octave Band ◽  
Band Noise ◽  
Lower Asymptote

Groups of monaural chinchillas trained in behavioral audiometry were exposed in a diffuse sound field to an octave-band noise centered at 4.0 k Hz. The growth of temporary threshold shift (TTS) at 5.7 k Hz from zero to an asymptote (TTS ∞ ) required about 24 hours, and the growth of TTS at 5.7 k Hz from an asymptote to a higher asymptote, about 12–24 hours. TTS ∞ can be described by the equation TTS ∞ = 1.6(SPL-A) where A = 47. These results are consistent with those previously reported in this journal by Carder and Miller and Mills and Talo. Whereas the decay of TTS ∞ to zero required about three days, the decay of TTS ∞ to a lower TTS ∞ required about three to seven days. The decay of TTS ∞ in noise, therefore, appears to require slightly more time than the decay of TTS ∞ in the quiet. However, for a given level of noise, the magnitude of TTS ∞ is the same regardless of whether the TTS asymptote is approached from zero, from a lower asymptote, or from a higher asymptote.

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