Simulation Analysis And Application Of Engine Noise Absorption And Insulation Material

As the rising of people's living standard, vehicles have entered millions of households as a common means of transportation. Now customers are getting to know more and more about the vehicles, which makes their equipments higher and higher. For a car, it has been concerned from the original price, changes to the present consideration, such as engine power, vehicle fuel economy, handling stability, ride comfort, appearance and interior and exterior styling, etc., which are the main factors to be considered when people buy cars. Meanwhile customers are becoming increasingly concerned about the NVH performance of vehicles, which even sometimes directly affect vehicle quality and customer satisfaction. Domestic manufactories have concern about automotive NVH performance mainly from the beginning of this century. Compared with foreign auto companies with hundreds of year's history, there is still a long way to go. For the vehicle NVH performance, the acoustical material is applied to solve the problem of vehicle vibration noise as a simple and effective way, and its application will not change the basic structure and layout of the original car, which makes more and more automobile companies and developers attach importance to the acoustical matetials.This paper is to study the performance of such an acoustical materials which is used to improve vehicle engine noise. This material is placed on the top of the engine to isolate and absorb the engine noise. This kind of material is formerly provided or technically instructed by foreign suppliers, so its price is very high. In order to reduce its costs, making the vehicle more competitive, we need to develop a cheap but good acoustical material to substitute the foreign material.In order to apply the acoustical materials in a reasonable and effective way, we must study the material absorption properties. This paper firstly summarizes the measurement methods of material absorption coefficient, such as reverberation chamber method, Alpha cabin method, standing wave tube, transfer function method, MLS method and so on. By indicating their respective characteristics and the application region, the foundation of the acoustical material measurement was built.In the study of acoustical materials, it was found that the sound-absorbing material mainly consists of two parts: the upper perforated aluminum panels and the lower composite fiber materials. The upper perforated aluminum panel can be approximated treated as a single-layer micro-perforated plate structure. In addition, we can give the best parameters to the lower fiber layer by means of structural analysis.In this paper, referring the well-known acoustic experts Ma Dayou 's micro-perforated plate theory, the micro-perforated panels for sound absorption structure were modeled and simulated. And the main factors that affect the sound absorbing ability was discussed in detail. After deciding the optimal parameters of structure and size, the detail optimization scheme was built. Then, the structural characteristic of substrate materials was analyzed, and the functions of foam, viscose and the wood fiber were discussed. On this basis, by further researching the micro-structure of the slit plate absorption properties, the corresponding improvement of the structure was recommended.By comparing the sound absorbing performances of the improved and other general materials, which were measured with standing wave tube method, it was confirmed the improved materials was better than the existing domestic acoustic materials. And its performance was very close to the foreign material.The materials used in the research were applied in vehicle noise control. The idle condition vehicle interior noise measurement and the pass-by exterior noise measurement showed that the sound-absorbing materials were effect to improving the interior noise, but had little effect on the exterior noise.