Sound Pressure Level Prediction And Main Source Analysis Of Heavy Duty Truck Interior Noise

China’s heavy duty truck industry has been becoming increasingly morecompetitive in the international market. However, there still exists a certain gapbetween the NVH(Noise, Vibration and Harshness) performance of the national heavyduty truck and the international advanced level. To research the prediction and analysismethods of heavy duty truck interior noise and develop heavy duty trucks with betteracoustic comfort is not only of strategic significance to China’s automobile industry,but also of great importance to China’s national economy.The research object of this dissertation is the cab of the heavy duty truck indevelopment. The goal is to build different acoustic simulation models of the cab forthe prediction of the vehicle interior sound pressure level in different frequency rangesand to build operational vehicle interior noise source contribution analysis model toanalyze the noise sources’ contribution. The purpose is to provide a platform toanalyze and optimize the vehicle interior sound field so that the NVH performance ofthe cab can be improved.Firstly, the analysis frequency range is determined according to the energydistribution of the measured vehicle interior noise. Then the finite element model ofthe body-in-white cab and the finite element model of the complete cab are builtconsequently. The models are validated with the modal tests of the body-in-white caband the complete cab. The results show that the models can be used in the followinganalysis and modeling.Based on the validated finite element model of the cab, the finiteelement-boundary element model is built with the integrated utilization of the finiteelement method and the boundary element method to predict the vehicle interior noisein the low frequency range. The hybrid finite element-statistical energy analysis modelis built with the integrated utilization of the finite element method and the statisticalenergy analysis method to predict the vehicle interior noise in the middle frequencyrange and the statistical energy analysis model is built to predict the vehicle interiornoise in the high frequency range. All these models are validated with the measureddata under different operational conditions. It shows that for the most part of theanalysis frequency range, the difference between the calculated value and the measured value is within5decibels.In the modeling process, the research emphasis is focused on the integratedutilization of available numerical calculation methods,the reasonable simplificationand modeling of different structures and junctions, the determination and definition ofconstraints and various excitations, the determination of statistical energy analysisparameters, and so on. A method to identify the acoustic characteristic parameters ofporous materials in semi-anechoic chamber is put forward, so that the acousticcharacteristic parameters of porous materials can be identified based on the directmeasurement of the whole material and porous materials can be acoustically modeledin the top-down design of the acoustic characteristics of the cab.Operational vehicle interior noise source contribution analysis model based on thetransmissibility concept is built. For the problem of the condition number of thereference excitation matrix changing with the frequency, a calculation method basedon the criterion of the minimal energy relative fitting error in every frequency is putforward, so that the transmissibility matrix can be calculated with more accuracy. Mainsources of vehicle interior noise under different operational conditions are determined.