Research On Sound Field Reconstruction And Separation Based On Helmholtz Equation Least Squares Method

The radiated noise of mechanical equipment contains a lot of information,and the measurement and analysis of radiated noise to identify the noise source can provide a basis for the design of vibration and noise reduction of the equipment.Near-field acoustic holography is widely used in the fields of noise source identification and fault diagnosis by measuring acoustic information and visualizing the sound field using sound field transformation algorithms.However,some shortcomings and problems are gradually exposed in engineering applications,including how to use small measurements In the face of large sound source surface,the sound field reconstruction,how to maximize the effective singular value after the singular value decomposition of the transfer matrix,and how to complete the sound field reconstruction in the presence of interference sources.In response to the above problems,this article has conducted the following research:(1)Starting from the basic theory of the least squares method of Helmholtz equation(HELS),an approximate solution of the radiated noise of the vibrating body is obtained,and for the ill-posed problem in the sound field reconstruction process,a new regularization method is proposed based on the existing regularization method The parameterized expression is transformed,the reference value is set by passing the singular value after matrix decomposition,the singular value smaller than the reference value is replaced,the singular value larger than the reference value remains unchanged,and the effective sound field information is retained to the maximum extent.The method is verified by numerical simulation and experiment.(2)The HELS method uses the superposition of basis functions to approximate the reconstruction of the sound field.It has high computational efficiency but involves many parameters.In order to improve the accuracy of sound field reconstruction,the control variable method is used to control the sound source spacing,sampling interval,number of basis function expansion terms,sound source frequency,and basis function Analyze parameters such as the origin and center position.(3)In order to solve the problem that it is difficult to reconstruct a larger source surface with a small measurement surface,the combined sound source and the thin plate sound source model are used as the simulation object to study the local near-field acoustic holography technology based on the HELS method,and the small holographic aperture is realized.The near-field extrapolation and reconstruction are compared with the traditional method.The results show that the reconstruction performance of the local near-field acoustic holography based on the HELS method is better than that of the traditional method.In order to solve the problem of the high reconstruction error of the HELS method at high frequencies,the acoustic radiation modal method and the HELS method are combined for sound field reconstruction.(4)The sound field containing interference sources was studied.The sound field separation method of single holographic surface measurement and double holographic surface measurement was used to separate the sound field and complete the reconstruction on the sound source surface.Compared with the result of direct reconstruction,the separated The reconstruction accuracy is high,and the reconstruction error of the sound pressure amplitude is small.(5)On the basis of numerical simulation,sound field reconstruction and separation experiments were carried out with the sound and fixed supported board as objects,which verified the sound field reconstruction algorithm in this paper.