Numerical calculation of the sound field focused by acoustic lens with an arbitrary axisymmetric sound speed distribution

2007 ◽  
Vol 54 (4) ◽  
pp. 823-829
Author(s):  
Xiang-hong Yan ◽  
Ya-ping Zhang ◽  
Ke-hui Liu ◽  
Yan Liu
Keyword(s):  
Numerical Calculation ◽  
Sound Speed ◽  
Sound Field ◽  
Speed Distribution ◽  
Acoustic Lens

scholarly journals A Spectral Method for Two-Dimensional Ocean Acoustic Propagation

2021 ◽  
Vol 9 (8) ◽  
pp. 892
Author(s):  
Xian Ma ◽  
Yongxian Wang ◽  
Xiaoqian Zhu ◽  
Wei Liu ◽  
Qiang Lan ◽  
...  
Keyword(s):  
Numerical Calculation ◽  
Spectral Method ◽  
Collocation Method ◽  
Approximation Error ◽  
Sound Field ◽  
Acoustic Propagation ◽  
Two Dimensional ◽  
Chebyshev Collocation Method ◽  
Chebyshev Collocation ◽  
Wide Range

The accurate calculation of the sound field is one of the most concerning issues in hydroacoustics. The one-dimensional spectral method has been used to correctly solve simplified underwater acoustic propagation models, but it is difficult to solve actual ocean acoustic fields using this model due to its application conditions and approximation error. Therefore, it is necessary to develop a direct solution method for the two-dimensional Helmholtz equation of ocean acoustic propagation without using simplified models. Here, two commonly used spectral methods, Chebyshev–Galerkin and Chebyshev–collocation, are used to correctly solve the two-dimensional Helmholtz model equation. Since Chebyshev–collocation does not require harsh boundary conditions for the equation, it is then used to solve ocean acoustic propagation. The numerical calculation results are compared with analytical solutions to verify the correctness of the method. Compared with the mature Kraken program, the Chebyshev–collocation method exhibits higher numerical calculation accuracy. Therefore, the Chebyshev–collocation method can be used to directly solve the representative two-dimensional ocean acoustic propagation equation. Because there are no model constraints, the Chebyshev–collocation method has a wide range of applications and provides results with high accuracy, which is of great significance in the calculation of realistic ocean sound fields.

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.

Improving Design of Muffler Based on Three-Dimension Numerical Calculation of Fluid and Sound Field

2011 ◽  
Vol 295-297 ◽  
pp. 2300-2303
Author(s):  
Hai Jun Zhao ◽  
Jia Dong Chang ◽  
Hong Jie Zhao
Keyword(s):  
Numerical Calculation ◽  
Environmental Pollution ◽  
Rotational Speed ◽  
Pressure Loss ◽  
Sound Field ◽  
Original Structure ◽  
Three Dimension ◽  
Vehicle Noise ◽  
Important Method ◽  
Aerodynamic Quality

Presence problem of exhaust muffler is anal sized, using three three-dimension numerical calculation of fluid and sound field improvement on original structure is performed, and improving results are certificated. It is shown that insert loss under every rotational speed all reach to the standard of 28dB（A）, and the noises of stationary end tube on the attention frequency band are all smaller than 5 dB（A） , and its pressure loss is decreased by about 32% than 7.6kPa of original structure muffler. So performance of the muffler is evidence increased, an important method is provided for decreasing whole vehicle noise, improving aerodynamic quality and reducing environmental pollution.

scholarly journals Breast Acoustic Parameter Reconstruction Method Based on Capacitive Micromachined Ultrasonic Transducer Array

Micromachines ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 963
Author(s):  
Yu Pei ◽  
Guojun Zhang ◽  
Yu Zhang ◽  
Wendong Zhang
Keyword(s):  
Computed Tomography ◽  
Time Reversal ◽  
Sound Speed ◽  
Ultrasonic Transducer ◽  
Reconstruction Method ◽  
Propagation Theory ◽  
Speed Distribution ◽  
Ultrasound Computed Tomography ◽  
Wide Range ◽  
Capacitive Micromachined Ultrasonic Transducer

Ultrasound computed tomography (USCT) systems based on capacitive micromachined ultrasonic transducer (CMUT) arrays have a wide range of application prospects. For this paper, a high-precision image reconstruction method based on the propagation path of ultrasound in breast tissue are designed for the CMUT ring array; that is, time-reversal algorithms and FBP algorithms are respectively used to reconstruct sound speed distribution and acoustic attenuation distribution. The feasibility of this reconstruction method is verified by numerical simulation and breast model experiments. According to reconstruction results, sound speed distribution reconstruction deviation can be reduced by 53.15% through a time-reversal algorithm based on wave propagation theory. The attenuation coefficient distribution reconstruction deviation can be reduced by 61.53% through FBP based on ray propagation theory. The research results in this paper will provide key technological support for a new generation of ultrasound computed tomography systems.

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 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.

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