Application Of Coherence Analysis Study On Identification Of Vehicle Noise Sources

With the development of automobile industry,the research on control noise inside the car has become the new study direction for major automobile manufacturers in order to improve the NVH performance of the vehicle better and to design,manufacture a car that conforms to the concept of modern consumers.It is a key link to effectively identify the noise sources that generate noise inside the car in the car manufacturing.In order to identify the noise sources that affect the noise in the vehicle,based on the theory of coherence analysis,the derivation and calculation of the coherence function was carried out.The conditions and the analysis flow of application of coherent and partial coherent functions were summarized.Vibration and noise test of vehicle was carried out by using LMS acquisition system.According to the car vibration and noise test standards,take a certain SUV model as the research object.The vibration acceleration in the left,the right and the rear suspensions passive side of the engine were laid,and sound pressure sensors in the intake system,the exhaust system,the engine compartment and the driver's right ear were laid.Real-time acquisition of multiple sets of idle and acceleration conditions passive side vibration acceleration and noise pressure date were obtained,the collect results will be used in common and partial coherence analysis.The time-domain data is processed to obtain the frequency spectrum of the vibration noise signal in the frequency domain,through the analysis of the noise spectrum in the car,the peak frequency of the noise in the car was determined,and compared with the vibration and noise spectrum of the noise source,the characteristics of the inside noise car and the noise sources were obtained.Combining with the test vehicle vibration and noise measuring point arrangement,a multi-input and single-output system model of coherence analysis was established.Coherent coefficients of noise sources and noise in vehicles were calculated respectively by common coherent and partial coherent analysis.The coherent coefficients are used to quantify the noise sources.The results show that the right suspension vibration is the main structural noise source under idling condition,followed by the engine noise.Under the accelerated conditions,the structural noise and air noise transfer to high frequency,the rear suspension is the main structural noise sources,the engine noise and exhaust noise are the secondary air noise sources.