Algorithms And Experimental Research For Near-field Acoustic Holography

Nearfield acoustic holography (NAH) is a robust tool for identifying noise sources and visualizing acoustic field. By multiplying the inversion of the calculated vibro-acoustic transfer matrix and the measured acoustic pressure vector on the hologram surface, the acoustic quantities (acoustic pressure, particle velocity), the acoustic intensity at arbitrary point and the acoustic power on arbitrary surface in three-dimensional acoustic field can be reconstructed. Nearfield acoustic holography (NAH) has been developed in the past two decade. The implementing algorithms of the NAH include the spatial transform of sound field (STSF), the boundary element method (BEM) and the Helmholtz equation least-square method (HELS). In this paper, to prove the results from our experiment that designed a (microphone array used in the experiment NAH frame and the metal sheets test used in the previous experiments STSF algorithm are effective-the implementation and enhancement of the STSF-based NAH have been developed. Then, the NAH based STSF has been used in noise source identification of fault simulation test bench, the experiment results demonstrate the effectiveness of NAH in noise source identification and of this application. The main contents include the following aspects:(1) Based on the review of the development of NAH and STSF, and analysis of the achievements and problems of recent related researches, we resolved those problems.(2) Based on the NAH technology of STSF, to address the key problems in the technic. The special functions and separations of variability are used to derive the theoretical formulations of plane NAH analyzed the error and discussed implementation of numerical algorithms.(3) Based on the NAH measurement, the analysis of the measurement processes, measuring instruments and features of measuring devices, a microphone array frame which use in NAH experiment has been designed. And the sheet metal exciting experiments demonstrated the effectiveness of STSF algorithm.(4) The NAH basic algorithm based on STSF have been used in noise source identification of fault simulation test bench. The experiment results demonstrated the effectiveness of NAH in noise source identification and pointed out the disadvantages in the application.(5) We concluded the full text and proposed the subjects of further studies. The process and results of this experiment have been concluded and the subjects of further studies in this paper.