Prediction and Identification of Vehicle Rattle Noise Caused by Shock Absorbers

A novel technology is proposed to predict vehicle rattle noise caused by shock absorbers. The shock absorber model is developed by analyzing the force of moving parts, hydronic characteristic of valves and physical characteristic of oil. The mount model is developed with the Maxwell method which combines series of spring and damping elements. The spring model is developed by curve interpolation of measured data, considering the hysteresis properties of the spring. The parameters of mass, wheelbase and tire etc. are measured and the vehicle body model is developed. The models of the shock absorber, mount, spring and vehicle body are combined together to develop the whole 4-wheel vehicle model to calculate the exciting forces of the shock absorbers. Furthermore, the transfer functions of sound pressure/force from the shock absorbers to the cabin are measured in real vehicle. The rattle noise is calculated using the exciting forces and the transfer functions. A modified gate filter is developed to reduce the background sound and extract the rattle noise, then the occurrence timing and conditions of the rattle noise can be identified easily and precisely.