Research On Internal Noise Source Identification Of Bmw New 5 Series

With the continuous development of contemporary automobiles,people have higher and higher requirements for the quality of automobiles.The quality of interior noise of automobiles has become a standard for consumers to choose automobiles.In order to occupy the market share of automobiles,automobiles that meet the requirements of consumers have been designed by all automobile factories,and more and more attention has been paid to the improvement of NVH performance of automobiles.In this paper,after automobile assembly,the road test of the product car in different road conditions is needed to detect the noise inside the car and determine the location of the noise source.The following research is carried out.Firstly,the generation mechanism and transmission path of automobile noise are elaborated,and several main noise sources are analyzed,thus several noise sources contributing more to the cab noise are determined.Next,according to the actual test situation of the whole vehicle factory and the test standard of vehicle noise and vibration,road test is carried out on the test vehicle.Acoustic sensors are located in the main noise sources of engines,gearboxes,exhaust systems,intake systems and tires to collect acoustic signals from several noise sources.Sensors are arranged in the driver's right ear and the passenger's right ear in the rear row to collect cab noise.Then,based on partial coherence theory and combined with the noise characteristics of BMW New 5 Series,a multi-input single-output system model is established.The auto-spectral density function and cross-spectral density function are used to process the collected acoustic signals,and the time-domain and frequency-domain analysis of the signals are carried out.Then the contribution of each system to the vehicle noise is calculated by using the partial coherence function.The results show that the partial coherence analysis method can accurately locate the noise sources in BMW 5 series car.Finally,the bus signals in the road test phase are intercepted and correlated to verify the results of the partial coherence analysis.At the same time,according to the characteristics of the research object,the relevant prospects are put forward.Because of the fast bus communication,the control unit can be installed to monitor the noise characteristics in real time..