On the basis of nearfield acoustic holography (NAH) based on the equivalent source method (ESM), patch NAH based on the ESM is proposed. The method overcomes the shortcoming in the conventional NAH that the hologram s...On the basis of nearfield acoustic holography (NAH) based on the equivalent source method (ESM), patch NAH based on the ESM is proposed. The method overcomes the shortcoming in the conventional NAH that the hologram surface should be larger than the source surface. It need not to discretize the whole source and its measurement need not to cover the whole source. The measurement may be performed over the region of interest, and the reconstruction can be done in the region directly. The method is flexible in applications, stable in computation, and very easy to implement. It has good potential applications in engineering. The nu- merical simulations show the invalidity of the conventional NAH based on the ESM and prove the validities of the proposed method for reconstructing a partial source and the regularization for reducing the error effect of the pressure measured on the hologram surface.展开更多
By the spherical wave spectrum transform,the sound pressures on the two spherical surfaces surrounding the scattering objects with arbitrarily-shaped sur-faces are decomposed into spherical wave components that propag...By the spherical wave spectrum transform,the sound pressures on the two spherical surfaces surrounding the scattering objects with arbitrarily-shaped sur-faces are decomposed into spherical wave components that propagate in a known manner,the relationships between the spherical wave components of the same order on the two spherical surfaces are established by the wave field extrapolation theorem,and the formula of the separation theory in the spherical coordinate is established in the wave-number domain. After separating the scattered pressure,the total scattered field can be obtained by holographic reconstruction and predic-tion. In order to overcome the instability of acoustic inverse problem,a new wave-number domain filter technique is proposed. It is proved that,as long as the two holographic spherical surfaces are taken to be close enough,the singularity of the separation formula can be avoided. The results of numerical simulation dem-onstrate the feasibility and validity of the separation theory.展开更多
A mathematical model of deterndulng sound power by using the scanning method is developed. It is assumed that the scanning speed is constant and the noise source is stationary The accuracy of estimating sound power al...A mathematical model of deterndulng sound power by using the scanning method is developed. It is assumed that the scanning speed is constant and the noise source is stationary The accuracy of estimating sound power along some simple paths on the surfaces such as rectangle, disc and hemisphere is analyzed. It is argued that the accuracy of estimating sound power is strongly depended on a suitable selection of scan path. The accurate estdriation of sound power can be made by scanning along some simple paths.展开更多
The regularization technique for stabilizing the reconstruction based on the nearfield acoustic holography （NAH） was investigated on the basis of the equivalent source method. In order to obtain higher regularizatio...The regularization technique for stabilizing the reconstruction based on the nearfield acoustic holography （NAH） was investigated on the basis of the equivalent source method. In order to obtain higher regularization effect, a regularization method based on the idea of partial optimization was proposed, which inherits the advantages of the Tikhonov and another regularization method-truncated singular value decomposition （TSVD）. Through the numerical simulation, it is proved that the proposed method is stabler than the Tikhonov, and more precise than the TSVD. Finally the validity and the feasibility of the proposed method are demonstrated by an experiment carried out in a semi-anechoic room with two speakers.展开更多
基金the National Natural Science Foundation of China (Grant Nos. 10504006 and 50675056) the Research Fund for the Doctoral Program of Higher Education (Grant No. 20060359003)
文摘On the basis of nearfield acoustic holography (NAH) based on the equivalent source method (ESM), patch NAH based on the ESM is proposed. The method overcomes the shortcoming in the conventional NAH that the hologram surface should be larger than the source surface. It need not to discretize the whole source and its measurement need not to cover the whole source. The measurement may be performed over the region of interest, and the reconstruction can be done in the region directly. The method is flexible in applications, stable in computation, and very easy to implement. It has good potential applications in engineering. The nu- merical simulations show the invalidity of the conventional NAH based on the ESM and prove the validities of the proposed method for reconstructing a partial source and the regularization for reducing the error effect of the pressure measured on the hologram surface.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 10504006 and 50675056)
文摘By the spherical wave spectrum transform,the sound pressures on the two spherical surfaces surrounding the scattering objects with arbitrarily-shaped sur-faces are decomposed into spherical wave components that propagate in a known manner,the relationships between the spherical wave components of the same order on the two spherical surfaces are established by the wave field extrapolation theorem,and the formula of the separation theory in the spherical coordinate is established in the wave-number domain. After separating the scattered pressure,the total scattered field can be obtained by holographic reconstruction and predic-tion. In order to overcome the instability of acoustic inverse problem,a new wave-number domain filter technique is proposed. It is proved that,as long as the two holographic spherical surfaces are taken to be close enough,the singularity of the separation formula can be avoided. The results of numerical simulation dem-onstrate the feasibility and validity of the separation theory.
文摘A mathematical model of deterndulng sound power by using the scanning method is developed. It is assumed that the scanning speed is constant and the noise source is stationary The accuracy of estimating sound power along some simple paths on the surfaces such as rectangle, disc and hemisphere is analyzed. It is argued that the accuracy of estimating sound power is strongly depended on a suitable selection of scan path. The accurate estdriation of sound power can be made by scanning along some simple paths.
基金supported by the National Natural Science Foundation of China(11004045,10974040)the Program for New Century Excellent Talents in University(NCET-08-0767)
文摘The regularization technique for stabilizing the reconstruction based on the nearfield acoustic holography （NAH） was investigated on the basis of the equivalent source method. In order to obtain higher regularization effect, a regularization method based on the idea of partial optimization was proposed, which inherits the advantages of the Tikhonov and another regularization method-truncated singular value decomposition （TSVD）. Through the numerical simulation, it is proved that the proposed method is stabler than the Tikhonov, and more precise than the TSVD. Finally the validity and the feasibility of the proposed method are demonstrated by an experiment carried out in a semi-anechoic room with two speakers.
