Study of a sound field separation technique based on a single holographic surface and wave superposition method

2009 ◽  
Vol 223 (8) ◽  
pp. 1827-1836
Author(s):  
W Q Jia ◽  
J Chen ◽  
C Yang ◽  
Z Y Wang
Keyword(s):  
Sound Pressure ◽  
Regularization Parameter ◽  
Sound Field ◽  
Mirror Image ◽  
Separation Technique ◽  
Tikhonov Regularization Method ◽  
Superposition Method ◽  
Wave Superposition ◽  
Measurement Surface ◽  
Field Separation

In order to overcome the limitation of traditional near-field acoustical holography (NAH), that the sound field on one side of the holographic surface must be free, a sound field separation technique based on single holographic surface and wave superposition method (WSM) is proposed. According to the WSM, the field on and near the measurement surface may be approximated by the field produced by virtual source points placed on a surface inside the structure. The source strengths are evaluated by applying boundary conditions on the measurement surface. Here, the ‘pseudo’ sound pressure of the reconstruction surface is first obtained based on the principle of sound field mirror image and WSM, then the sound pressure of the target sound source acting on the holographic surface is separated by the sound pressures of the holographic surface and the reconstruction surface, and the sound field separation is realized. The technique requires the inversion of the Green's function matrix, which may be ill-conditioned. The Tikhonov regularization method is used to invert it, and the value of the regularization parameter is determined by the L-curve criteria. Through the numerical simulation and experiment, the results show the validity and efficiency of this technique.

STUDY OF SOUND SOURCE IDENTIFICATION BASED ON BEAMFORMING AND PATCH NEAR-FIELD ACOUSTIC HOLOGRAPHY

2009 ◽  
Vol 17 (03) ◽  
pp. 219-245 ◽  
Author(s):  
WENQIANG JIA ◽  
JIN CHEN ◽  
CHAO YANG ◽  
JIAQING LI
Keyword(s):  
Regularization Parameter ◽  
Near Field ◽  
Sound Field ◽  
Reconstruction Error ◽  
Tikhonov Regularization Method ◽  
Superposition Method ◽  
Sound Sources ◽  
Extrapolation Technique ◽  
Measurement Surface ◽  
Data Extrapolation

A study for applying data extrapolation technique based on wave superposition method (WSM) is proposed to overcome the disadvantages of near-field acoustical holography (NAH). Unlike conformal NAH, where the measurement surface surrounds the entire structure, in the patch holography the measurement surface needs only be approximately as large as the patch on the structure surface where the reconstruction is required. At first, a microphone array is used to acquire the sound pressure field radiated from a vibrator; then a beamforming method is adopted to locate sound sources; after that, a serial of equivalent sources are collocated around these sound sources; at last, a data extrapolation technique based on WSM is applied to extend the measurement aperture and reconstruct the sound field. Since the data extrapolation algorithm requires the inversion of Green's function matrix which may be ill-conditioned, Tikhonov regularization method is used to invert it, and the value of the regularization parameter is determined by the L-curve criteria. The effectiveness of this method is demonstrated by numerical simulation with two pulse ball model, and also experiment is carried out in a semi-anechoic chamber using two sound boxes. The results confirm that the exterior sound field can be accurately reconstructed with few iterative times and the reconstruction error is sufficiently suppressed by the proposed method.

Active control of the scattered radiation with a reflecting surface

2019 ◽  
Vol 67 (3) ◽  
pp. 190-196
Author(s):  
Ning Han
Keyword(s):  
Control System ◽  
Active Control ◽  
Scattered Radiation ◽  
Sound Pressure ◽  
Sound Field ◽  
Control Area ◽  
Mirror Image ◽  
Three Dimension ◽  
Control Effect ◽  
Reflecting Surface

Based on a prediction method of the scattered sound pressure, an active control system was proposed in previous work for the three-dimension scattered radiation, where all the relevant simulations and experiments were implemented in three-dimensional free sound field. However, for practical applications, such as the anti-eavesdropping system or the stealth system for submarines, the sound field conditions are usually complex, and the most common case is the one with reflecting surface. It is questionable whether the previous control system is still effective in non-free sound field, or what improvements should be operated to ensure the control effect. In this article, based on the mirror image principle, two methods of calculating the control source strengths are proposed for the scattered radiation control, and numerical simulations with one-channel and multi-channel system are implemented to detect the corresponding control effect. It is seen that the local active control for the scattered radiation is still effective, and the reduction of the sound pressure level as well as the control area is extended with the increasement of the error sensors and control sources.

Simulation and experimental investigations for the patch near-field acoustical holography

2008 ◽  
Vol 222 (6) ◽  
pp. 945-953 ◽  
Author(s):  
C Yang ◽  
J Chen ◽  
J Q Li ◽  
W F Xue
Keyword(s):  
Fourier Transform ◽  
Sound Pressure ◽  
Near Field ◽  
Sound Field ◽  
Experimental Investigations ◽  
Regularization Methods ◽  
Aperture Size ◽  
Measurement Surface ◽  
Physical Necessity ◽  
Acoustical Holography

In order to reconstruct the sound field, the fast Fourier transform (FFT)-based near-field acoustical holography (NAH) demands that the measurement surface must extend to a region where the sound pressure decreases to a low level. This method is unfit for reconstructing the partial sound field in which the measurement aperture size is limited either by physical necessity or as a way of reducing the measurement cost. Statistically optimal NAH (SONAH) performs plane-to-plane calculations directly in the spatial domain, avoids all errors occurred in the FFT-based NAH and significantly increases the accuracy of the reconstruction of the partial sound field. In the present work, combined with the different regularization methods, SONAH is performed for reconstructing the partial sound field. The errors over the central and the peripheral sections of the reconstruction area are researched separately. Simulations and experiments show that SONAH is successful in reconstructing the partial sound field and the errors over the central sections are smaller than that over the peripheral sections. Experiments demonstrate that Tikhonov regularization in conjunction with Engl's criterion is suitable for the reconstruction of the practical sound field.

scholarly journals The principle of statistically optimal planar near-field acoustical holography and the sound field separation technique

2005 ◽  
Vol 54 (3) ◽  
pp. 1253 ◽  
Author(s):  
Li Wei-Bing ◽  
Chen Jian ◽  
Yu Fei ◽  
Bi Chuan-Xing ◽  
Chen Xin-Zhao
Keyword(s):  
Near Field ◽  
Sound Field ◽  
Separation Technique ◽  
Acoustical Holography ◽  
Field Separation

Development of Near-Field Acoustical Holograph and its Review

2014 ◽  
Vol 971-973 ◽  
pp. 1598-1601
Author(s):  
Xu Liu ◽  
Xiao Qin Liu ◽  
Chang Liu
Keyword(s):  
Near Field ◽  
Sound Field ◽  
Separation Technique ◽  
Acoustic Holography ◽  
Noise Sources ◽  
Engineering Applications ◽  
Powerful Technique ◽  
Experiment And Simulation ◽  
Acoustical Holography ◽  
Field Separation

Near-field acoustic holography (NAH) is a powerful technique for identifying noise sources and visualizing acoustic field.The theory and algorithm of NAH techniques are introduced , and it is proved by experiment and simulation. The researches on near field acoustical holography (NAH) are reviewed，including the sound field separation technique and Patch NAH technique arisen in recent years.The difficulties in NAH and research on current situations are discussed , Finally,some engineering applications are introduced by detailed examples.

scholarly journals A sound field separation technique based on measurements with pressure-velocity probes

2009 ◽  
Vol 125 (6) ◽  
pp. 3518-3521 ◽  
Author(s):  
Yong-Bin Zhang ◽  
Xin-Zhao Chen ◽  
Finn Jacobsen
Keyword(s):  
Sound Field ◽  
Separation Technique ◽  
Field Separation
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