A Study on Holographic Reconstruction of Cyclostationary Sound Field Based on Boundary Element Method

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
H. B. Zhang ◽  
Q. Wan ◽  
W. K. Jiang ◽  
C. J. Liao
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Modulation Frequency ◽  
Sound Field ◽  
Special Kind ◽  
Frequency Component ◽  
Vibrational Signal ◽  
Spectral Density Functions ◽  
Ill Posed ◽  
Element Method

The cyclostationary vibrational signal modulated by other signals can be considered as a special kind of nonstationary signal, which is found frequently in some rotating machinery. The modulation frequency component can be extracted from the total signal using second-order cyclic statistics at the appropriate cyclic frequency. By using the cyclic spectral density functions instead of power spectrum or spectrum as the variables, the cyclostationary nearfield acoustic holography (CYNAH) technique is used to reconstruct acoustic physical quantities in the cyclostationary sound field. In this presented work the CYNAH method is combined with the boundary element method (BEM) to overcome the limitations on the geometries of the planar CYNAH method. The methods used in the conventional BEM-based NAH to overcome nonuniqueness and the ill-posed nature should be also implemented here. The results of a simulation show satisfactory agreement between the computed values and the analytical ones.

516 Analysis of 3-Dimensional Sound Field by the Boundary Element Method

2000 ◽  
Vol 2000.53 (0) ◽  
pp. 155-156
Author(s):  
Koji MATSUMOTO ◽  
Yoichi KANEMITSU ◽  
Shinya KIJIMOTO ◽  
Koichi MATSUDA
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Sound Field ◽  
3 Dimensional ◽  
Element Method

scholarly journals Sound field study of a building near a roadway via the boundary element method

2017 ◽  
Vol 37 (3) ◽  
pp. 519-533 ◽  
Author(s):  
Haibo Wang ◽  
Ming Cai ◽  
Shuqi Zhong ◽  
Feng Li
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Insertion Loss ◽  
Sound Field ◽  
Road Traffic Noise ◽  
Heavy Vehicles ◽  
Main Frequency ◽  
Aspect Ratios ◽  
Hankel Functions ◽  
Element Method

A two-dimensional boundary element method with a constant element type was adopted to study the sound field of a building near a roadway. First, a factor analysis of the computed results has been done, which include the element length, the Hankel functions’ calculation accuracy, and numerical integration accuracy. Then, boundary element method is applied to calculate building attenuation with different building aspect ratios and different frequencies with balconies, followed by drawing of the sound field distribution diagram. The calculation results revealed the following: (1) a wider building results in a more severe sound attenuation; (2) balconies on different floors produce a reduction of approximately 15 dB for broadband spectral characteristics of A-weight road traffic noise, and the maximum values appear at the bottoms of balconies; (3) for the points in the balconies, higher sound frequencies are correlated to larger insertion loss, with the insertion loss increasing from 3 dB to >10 dB when the sound frequency increases from 20 to 4000 Hz; (4) calculations of three typical frequencies indicate that the insertion loss of 500 Hz (main frequency of heavy vehicles) is 6 dB less than that of 800 Hz (main frequency of light vehicles), i.e. the flow control of heavy vehicles could conspicuously improve the ambient acoustic environment of buildings near a roadway.

scholarly journals Reconstruction of transient pressure and acceleration over a tire surface using the inverse time domain boundary element method

2019 ◽  
Vol 283 ◽  
pp. 04014
Author(s):  
Yang Zhang ◽  
Chuanxing Bi ◽  
Xiaozheng Zhang ◽  
Yongbin Zhang ◽  
Liang Xu
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Time Domain ◽  
Domain Boundary ◽  
Sound Field ◽  
Rigid Sphere ◽  
Transient Pressure ◽  
Retarded Time ◽  
Reconstructed Surface ◽  
Element Method

The inverse time domain boundary element method (ITBEM) that is derived from the direct time domain boundary element method by eliminating the retarded time is able to reconstruct the transient pressure and flux on the surface of an arbitrarily shaped source by measuring the pressure on a hologram surface. In the present work, the ITBEM is applied to reconstruct the transient pressure and acceleration over the surface of a tire which is supported away from the ground in a semi-anechoic chamber. The tire is impacted by a rigid sphere to generate a transient sound field, and the measurement is controlled by a trigger which is connected to an acceleration sensor stuck on the surface of the tire. The pressure and acceleration on the surface of the tire are reconstructed from the holographic pressure measured by array microphones. By visualizing the pressure and acceleration with respect to the elapsed time, the wave propagation phenomenon of the pressure and acceleration on the surface of the tire is shown clearly. The comparison of the reconstructed surface acceleration to the measured one demonstrates the effectiveness of ITBEM for transient sound field reconstruction.

Inverse Identification of Heat Boundary Conditions for 2-D Anisotropic Coating Structures

2011 ◽  
Vol 130-134 ◽  
pp. 1825-1828
Author(s):  
Huan Lin Zhou ◽  
Hu Sha Han ◽  
Chang Zheng Cheng ◽  
Zhong Rong Niu
Keyword(s):  
Boundary Element Method ◽  
Singular Value Decomposition ◽  
Boundary Conditions ◽  
Boundary Element ◽  
Singular Integrals ◽  
Singular Value ◽  
Thin Body ◽  
Ill Posed ◽  
Value Decomposition ◽  
Element Method

The singular value decomposition is employed to identify heat boundary conditions for 2-D anisotropic coating structures. The boundary element method is applied to analyzing the model. The nearly singular integrals in the boundary element method for thin body problems are dealt with by the analytical integral formulas. The ill-posed system is treated by the truncated singular value decomposition technique. Numerical example demonstrates the effectiveness and accuracy of the present algorithm.

A TECHNIQUE FOR PLANE-SYMMETRIC SOUND FIELD ANALYSIS IN THE FAST MULTIPOLE BOUNDARY ELEMENT METHOD

2005 ◽  
Vol 13 (01) ◽  
pp. 71-85 ◽  
Author(s):  
Y. YASUDA ◽  
T. SAKUMA
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Large Scale ◽  
Numerical Study ◽  
Sound Field ◽  
Field Analysis ◽  
Fast Multipole ◽  
Plane Symmetric ◽  
Sound Fields ◽  
Element Method

The fast multipole boundary element method (FMBEM) is an advanced BEM, with which both the operation count and the memory requirements are O(Na log b N) for large-scale problems, where N is the degree of freedom (DOF), a ≥ 1 and b ≥ 0. In this paper, an efficient technique for analyses of plane-symmetric sound fields in the acoustic FMBEM is proposed. Half-space sound fields where an infinite rigid plane exists are typical cases of these fields. When one plane of symmetry is assumed, the number of elements and cells required for the FMBEM with this technique are half of those for the FMBEM used in a naive manner. In consequence, this technique reduces both the computational complexity and the memory requirements for the FMBEM almost by half. The technique is validated with respect to accuracy and efficiency through numerical study.

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