Research On Analysis And Control Of Car Interior Noise Based On SEA Method

The research and the application of car NVH characteristics are developing, now. The object of research can be the characteristics of the whole or part car. The research level in China lags much behind the overseas'. The domestic research also focuses on the match of powertrain and the optimization of autobody rigid in low frequency range, and so on. The analysis of car NVH characteristics in mid and high frequency based on SEA method is developing in China now. The research of this thesis is developed with the support of the Scientific and Technological Planning Project of Jilin province"Analysis and Control of Car Interior Booming and Aerodynamics Noise"(20040332-1)and the National"863"Project"The Analysis and Control of Interior and Exterior Mid-high Frequency Noise of Car from Powertrain Mounts, Air-intake and Exhoust"(2006AA110102-3). Based on a domestic car and the research of Prof. Wang's group, the research on analysis and control the car interior noise using SEA method was done. The aerodynamic pressure is the important content of analysis. Some control ways about reduction the noise of driver's head cavity were put forward based the sensitive panels of power inputs to driver's head cavity. A new concept of SPL (Sound Pressure Level) reduction efficiency of noise control was put forward, too. The best way to reduct the noise of driver's head cavity was found by the synthesis balance validated by testing. The research of this dissertation completes the control techniques of car mid-high frequency noise. The power inputs of the car SEA model about high frequency noise control were also defined actually. And, the research of this thesis can be as an effective method to value the interior noise control, because it has important engineering meanings.A CAD model of a domestic car was built. Then, the divided way of all subsystems was decided by the theory of modes similitude. The occupant cavity and trunk cavity were also built. All the panels of the autobody were built as plats subsystems, singuly curved shells subsystems or doubly curved shells subsystems. The beams structures were built as beams subsystems those can bend or torque. The total is 81 structures subsystems and 6 sound cavities subsystems, those have the statistical characteristics. Engine, suspensions and tyres are not included in the SEA model, but their inputs to the autobody were directly put at the right position. All the subsystems were given their physic properties, such as materials, rotatory radius, and so on. The junctions should be built after the subsystems construction among the subsystems, those are very important to complete the processes, such as depositing, transfering and wasting the energy among the subsystems.Modes density, damping loss factor (DLF) and coupling loss factor (CLF) are three important parameters of SEA. The precision of the three parameters can directly affect the prediction and the control of the interior noise and vibration level. The modes density, DLFs and CLFs of regular subsystems can calculate using the theory method. Generally, DLFs are looked as the main sources of the deviation of system dynamics simulation. The DLFs of the complicated subsystems can be obtained by the respective testing to measure the energy loss of the uncoupled structures. The CLF is the important unique parameter of SEA method. The CLFs among the coupling subsystems can be obtained by theoretical calculation using the analysis of wave propagation. Sometimes, testing is used to get the CLFs if the theoretical calculation is not convenient.The power inputs of this thesis can also be acquired by the theory and testings. The inputs include the vibration from powertrain to autobody on powertrain mounts and the sound radiation in engine bay, the aerodynamics pressure on the autobody surface, the inputs from roads random excitations and tyres vibration on the suspensions house to the structures, and so on. The aerodynamic pressure is the important analysis content of SEA model in the thesis. The powertrain vibration to structures and the sound radiation in engine bay to the interior sound cavity are looked as the important noise sources those can measure by the actual testing. The aerodynamics pressure on surfaces and the inputs from roads random excitations and tyres vibration on the suspensions house to the autobody are also important noise sources those can be got by simulation by software systems. The accurately inputs are the key to simulate the sound pressure level of driver's head cavity.The SPL of driver's head cavity can be predicted by the of SEA simulation. The validity of the SEA model can be validated by the contrast analysis between the simulation results data and the testing measure data at driver's ear. This is the assurance of the proceeding control analysis of driver's head cavity noise.The sensitive panels of driver's head cavity can be pointed by the analysis both unit power inputs and actual power inputs of the subsystems to the driver's head cavity. They are the theoretical bases and direction indicators for the farther noise control and optimization. Some noise control way of driver's head cavity were put forward based these sensitive panels.A new concept of SPL reduction efficiency of noise control was put forward, which can be looked as the key target to evaluate the effects of the noise control measures. Totally, there are 3 groups including 11 control ways. So, the most effective control way to reduce the SPL of driver's head cavity was pointed by the reduction efficiency of noise control, which is the important reference. It has important engineering significance because it can be looked as an effective evaluation method for car interior noise control in mid-high frequency. The real car testing about optimized noise control to reduce the driver's head SPL validated the simulation results, which also proved the validity of noise reduction way by SEA simulation predict. It has important engineering practical value.The research shows the sound performance of driver's head cavity can be effective controlled using SEA method aimed at different frequency band if the right control way implemented. An application method to improve the performance of car interior noise was brought forward based on SEA method in the early phase of new car development and the modification of existing car styles.