The Study On Simulation Methods Of The Door-Slamming Noise In A Passenger Car

The door-slamming sound quality of a car directly affect the decision of the customers whether to buy it. There are a lot of factors affecting the door-slamming sound quality, mainly include:lock structure, glue sstructure, the plate structure of the door and so on. At present, the sound quality evaluation methods of door-closing can be divided into subjective evaluation and objective evaluation. Through the subjective evaluation experiment, we can rate the sound quality of door slamming. After the objective evaluation experiment, the psychological parameters (loudness, sharpness) which can evaluate the soud quality of door-slamming would be obtained. Both of the subjective and objective evaluation methods are adopted after producing the sample vehicle, and based on experimental means. But we still lack the methods used before producing the sample vehicle to evaluate the sound of door slamming. The design of the noise reduction of vibrating plate already becomes an important content of automotive engineering designs. Through the optimizing design of reducing vibration and noise of the door plates, we can do some quantitative changes of the design model to achieve the desired effect of vibration and noise reduction in the design stage. Supported by the project with the enterprise cooperation "Structure Design of Door System ", this thesis established a design process and method in order to reduce the sound pressure level of door-slamming by modifying the structural parameters of the door plates. The mainly works are list as follow:1) As the thicknesses of the door plates which are among the structural parameters of door system directly affect the sound of door-slaming are important and easy to be changed, at first, we built a response surface model with the thicknesses as design variables and the objective of minimizing the root meam square of kinetic energy in the process of closing door, and then, we optimized the model by genetic algorithm, at last, we got a new set of thicknesses of the door plates after the optimization.2) In order to verify the noise radiated out from the optimized plates is less than before the optimization, we did some numerical analysises of the sound pressure level radiated out from the original plates and the optimized plates by the acoustic radiation boundary element method based on pulsed excitation, and then, we compared the noises. The results show that we achieved the noise reduction by the optimization. 3) Based on the actual situation, the enterprise produced two sample cars. One of the cars had the same thicknesses of door plates with the model before the optimization, there are only 0.2mm difference between the other one and the optimized model. In order to evaluate the sample cars's sound quality of door-slamming, we got a car with good sound quality as the benchmark car. After make a sound quality experiment, we got the loudness, sharpness, sound pressure level with A-weighted and one-third octave to evaluate the two sample cars and the benchmark car. The experimental results show that the modified car had lower loudness, sharpness and sound pressure level with A-weighted than before, the modified car's sound quality of door-slamming have reached the level of benchmark car, which proved the process of structural optimization described in this thesis aiming to reduce the noise of door-slamming is feasible and correct.