Rattle noise assessment of vehicle suspension dampers via road testing

The aim of this work is to examine structure-born noise occurring in vehicle suspension systems with conventional passive double-tube shock absorbers. The particular structure-born noise is known as rattling within the automotive industry. Double-tube shock absorbers have dominated the passive suspension systems market. Therefore, it is extremely important to understand such performance degrading phenomena. The rattling phenomenon has origin in the interactions between the valve(s) and the fluid passing through them. The resulting vibrations propagate through the vehicle’s structure and are perceived by vehicle occupants as an unpleasant noise with a distinct frequency content. It is known to degrade the perception of the (otherwise acceptable) performance of the vehicle. So far, in their assessment efforts of the rattling phenomenon vehicle OEMs (Original Equipment Manufacturers) or automotive damper manufacturers have relied on road tests on dedicated test tracks and employing skilled test drivers. However, the efforts are expensive and time-consuming. In the paper the authors present the results of a series of road tests on selected road surfaces with an aim to assess the rattling performance of several suspension double-tube damper units and relate them to laboratory data for the purpose of cost reduction and accelerating the suspension development process. The road test results are supported by laboratory tests by means of dedicated test rigs to provoke the rattling phenomenon. In general, the laboratory tests show a good correlation with the vehicle data. The obtained results yield evidence that the laboratory test setup and conditions can be used for reproducing the rattling phenomena in the controlled environment. To demonstrate that, the authors tested reference damper units in parallel with dampers having a modified component in the base valve; the magnitude of reduction of the measured rod acceleration is higher in laboratory tests than in the case of the road tests on selected surfaces. In general, the results provide a valuable feedback for vehicle modeling studies to be undertaken by the authors in some near future and a confirmation of the usefulness of the laboratory procedures for the rattling noise investigations.