A Car Interior Noise Identification And Control Based On Advanced Transfer Path Analysis

The car interior noise characteristic is an important index of vehicle ride comfort performance.Transfer path analysis(TPA),as an effective technique to solve the problem of vehicle noise,and improve the performance of NVH,has been developed in a wide range of engineering applications.Among the researches in TPA field,some TPA methods have been proposed and applied,such as conventional TPA(CTPA),operational TPA(OTPA).These methods have each their own advantages and applications,but also faced with the contradiction between the accuracy and workload.This thesis researched a new kind of transfer path analysis method-Advanced transfer path analysis(ATPA).This method is a test-based numerical technique allowing the diagnosis necessary to solve vibro-acoustics problems.There is no need to remove the source of excitation,at the same time,it can separate and quantify the path of transmission,proved to be a transfer path analysis method with high precision and efficiency.For the first application to the interior noise of a small SUV,the transfer path analysis is conducted via ATPA to recognize the major contribution paths.Combined with the experiment and simulation method,this paper researched the interior noise characteristic,finally taking effective and reasonable measures for noise reduction.The main contents are as follows:1,Introduced the principle and classification of TPA.Based on the actual situation of this project,the theoretical basis and the process of the experiment of ATPA are emphasized.Aiming at the different frequency characteristics of the excitation source,ATPA method based on the coherence method is adopted to study the low frequency noise of idling condition in the car,and the high frequency noise is researched via ATPA method based on the energy method under the 60km/h constant speed condition.2,Analyzed the source and its mechanism of all kinds of noise in the car.Considering the cross-coupling of the transfer paths,established the ATPA model of the driving cabin noise in the condition of idling speed and 60km/h constant speed.3,Apply the ATPA theory to the practice of automobile noise reduction.Based on the ATPA model,ATPA theory is used to carry out the ATPA test under the two common condition.In the first step,the Global Transfer Functions(GTFs)are measured and the Direct Transfer Functions(DTFs)are calculated from them.In the second step,the dynamic signal is measured under the desired operational conditions and the contributions from subsystems towards objective points are calculated.The results show that the maximum contribution of the interior noise is from the exhaust system under the idle speed condition.Under the 60km/h constant speed condition,the main contribution of the interior noise is from the front windscreen and the engine radiation noise.4,According to the test results,the corresponding optimization measures are adopted to improve the interior noise level.Through the modal analysis on the exhaust system,there is no coupling between the incentive and exhaust system.Using the average driver freedom displacement method for the best position of the exhaust lug,finally the optimization scheme is determined to remove the back of the lug forwards 10.0 cm.And the test found that the driving cabin noise decreased significantly under the idle speed condition.As for the high frequency noise at the 60km/h constant speed condition,the front windscreen is changed to 6mm on the basis of the original.The engine room is equipped with sound damping material,and finally the cabin noise is reduced by 1.9d B(A)at constant speed of 60km/h condition,achieved the expected noise reduction effect.