NVH Test Rig Acoustic Field Characteristics Analysis And Optimal Design Based On Semi-anechoic Chamber

NVH test rig has been widely used in relevant domestic enterprises and research institutes, and its testing acoustic field has an important influence on obtaining NVH test dates. Thorough research of the acoustic field of NVH test rig has great significance to improving the research and design level of domestic NVH test rig, perfecting the test method in NVH test and promoting the development of NVH test equipment technology in China. Therefore, aiming at the development status of domestic NVH test rig technology and the needs of the theoretical study and practical project, based on a composite board semi-anechoic chamber, this dissertation makes a systematic research on the acoustic field of NVH test rig to establish an analysis and evaluation method for acoustic field of NVH test rig and perfect the design method of NVH test rig on the acoustic.Firstly, the composition systems and development history of NVH test rig were introduced, and the previous research work at home and abroad were summarized, and then found that there were no systematic research on the acoustic field characteristic of NVH test rig. In order to explore the acoustic field characteristic of NVH test rig, the acoustics theory and the corresponding assumptions were summarized and analyzed, combined with the imagine source method and the ray tracing method, a new sound propagation model and a half-free acoustic field model were gotten by deriving the sound propagation model of a spherical sound source. Secondly, based on acoustical finite element method, an acoustic finite element model was established on the low-medium frequencies; based on the imagine source and the ray tracing hybrid method, a half-free acoustic field model was established on the medium-high frequencies. And then a set of analytical methods were provided for further studies on the acoustic field characteristics of NVH test rig by analyzing the free field range and verification test. Thirdly, based on a composite board semi-anechoic chamber, when an obstacle like testbed shielding was inserted in the acoustic field, a comparative analysis about the free field range has been carried on. Finally, in the acoustic field, in which a testbed shielding was inserted, height of the sound source and testbed shielding were parametrically analyzed, which had an influence on the acoustic field distribution characteristics, and also the corresponding evaluation indexes were proposed. At the same time, based on acoustical finite element method, the height of regular hexahedron testbed shielding was parametrically optimized by using one dimensional search method. And which became an acoustic reference for the design of NVH test rig.Through the research above all, an analysis and evaluation method for acoustic field of NVH test rig was established, which provided methodological guidance for establishing the acoustic evaluation and acceptance method of NVH test rig, and improved the design method of NVH test rig based on acoustic.