A Study On New Methods For The Analysis Of The Sound Field Radiated By A Machine

In this dissertation, the numerical computation for the acoustic radiation problem (ARP) is studied deeply and systematically in the theory, method and the application technique, based on analyzing the situation of the home and abroad on the numerical computation for the acoustic radiation problem.The calculation formulas of the boundary element method (BEM) for the exterior acoustic radiation problem in the full-space and half-space are deduced, based on the wave propagation theorem; The arising of the non-unique solutions, which is associated with the application of the boundary integral equation (BIE) in acoustic radiation problem, is analyzed and proofed; The Improved Combined Helmholtz Integral Equation Formulation (ICHIEF) is presented to overcome the non-uniqueness problem more effectively and reliably; The determination of the singular integral coefficients on various occasions is analyzed; The properties and treatments of the singular integrals with different orders axe studied; The computation program of the cubic spline ICHIEF is developed and its ability to overcome the non-uniqueness problem and feasibility to discrete the surface coarsely with the sufficient calculation precision are examined through examples.The formulation for the error analysis of acoustic radiation problem calculated by the boundary point method (BPM) is put forward; The physical explanation of the boundary point analysis of the acoustic radiation problem is given; The influence of the particular solution on the calculation stability of the BPM is studied; The etthanced volume source boundary point method (EVSBPM) is presented; A test for the effectiveness of the EVSBPM is carried out on the aspects of its calculation precision, calculation speed, calculation stability, adaptation to the geometric shape of vibrating body as well as its ability to overcome the non-uniqueness problem through various examples with different boundary shapes and different boundary value distributions.A new kind of numerical method, the statistical distributed source boundary point method (SDSBPM), used to calculate the acoustic radiation problem caused by the random vibrating body is presented; A test for the effectiveness of the SDSBPM is carried out on the aspects of its calculation precision, adaptation to the geometric shape of vibrating body as well as its ability to overcome the non-uniqueness problem through various examples with different boundary shapes and different boundary value distributions.A rectangular box simulating the axial box of the lathe tool is manufactured; Experimental measurements of the surface vibration on the rectangular box and the acoustic field around the rectangular box corresponding to firstly a series of a homogeneous excitation and secondly twoIIIindependent white noise excitations are taken in a semi-anechoic chamber. Taking the vibratory properties as input, the properties of the sound field are calculated by the EVSBPM and the SDSBPM respectively. The effectiveness and reliability of the EVSBPM and the SDSBPM for the calculation of acoustic radiation problem is further verified from the comparison of the calculated results and measured ones.