Research On Identification Of Noise Source And Comprehensive Control Technology In Passenger Car

The NVH performance of a vehicle affects the ride quality as well as the survival and development of automobile enterprises,and it is of practical significance for the diagnosis and control of vehicle noise.Based on the NVH performance improvement project of a new brand MPV,this paper studies the noise analysis method and noise control technology and strategy in order to solve the problem of abnormal noise and improve the sound quality in the vehicle.The practice of the noise control has certain reference significance for automobile NVH control.The main research contents are as follows:(1)Analyze the present situation of NVH development in the automotive industry,and point out that there is insufficient research and development control in the early stage of NVH research and development,which leads to many NVH problems in the later period of automobile product development.(2)The noise source of traditional and new energy vehicles are analyzed firstly.And then the principles of various automobile noise diagnosis techniques are summarized and studied.The traditional diagnostic methods and modern diagnostic methods(such as spectrum analysis,short-time Fourier analysis,order analysis,wavelet analysis,TPA)are discussed respectively combining with engineering examples,which lay the theoretical foundation for the practice of noise diagnosis.Among them,spectrum analysis,time-frequency analysis and order analysis are widely used in NVH testing.(3)Focusing on a new domestic MPV,the main noise source and the amplification path are identified by the diagnosis methods of time-frequency,order,NTF,modal analysis and so on,pointing out the direction for the interior noise control.(4)On the basis of elaborating the theory and principle of automobile vibration and noise propagation,influencing factors such as mass,stiffness,damping,vibration isolation,dynamic vibration absorption and noise source matching,are discussed on their influence(5)mechanism,advantages and disadvantages and application areas,which lays the foundation on the control engineering program of interior noise.Using the basic principles and methods described above and considering the actual effects,cost and engineering practicability,compre-hensive control of the noise in the vehicle is carried out: ?increase the thickness of the front damping plate,solving the booming problems caused by the second engine order noise during3200-3300rpm;?the tire modal frequency drops to 94 Hz by modifying the tire structure;?reduce the fifth gear ratio appropriate in the the premise of power.Eventually,the total sound pressure level decreases by about 5dB,and the modulation phenomenon is successfully eliminated,enhancing the car sound quality significantly.