Low frequency road noise decomposition at wheel center on an roller bench

Various methods can be used to achieve a better understanding of road noise propagation from the road to passengers’ears. This paper deals with a decomposition of the low frequency structure-borne noise transmission paths at the wheel center in order to assess tire/wheel and vehicle effects. It has been performed jointly by a car and a tire manufacturer. This decomposition involves blocked forces and vibroacoustic frequency response functions, both requiring specific setups to be measured on a roller bench. As road noise is a random process, a principal component analysis has to be performed on tire/wheel blocked forces to properly handle dynamic excitations. Since the interface between wheel and suspension is rather stiff, the quality of tire/wheel blocked forces measurement strongly rely on bench test characteristics. In addition, comparisons between results coming from tire and car manufacturers may be distorted due to differences of road surfaces of rollers. Another difficulty is related to rotating effects that can’t be neglected and which can alter the quality of the road noise recomposition. One challenge still remains to measure transfer functions in operating conditions. When handled with care, those items lead to pretty good results. Tire/wheel and vehicle effects on interior road noise can then be separated.