Previous studies have shown correlations between the properties of multi-asperity road surfaces and CPX noise spectra below 1000 Hz. Noise increases when the mean distance and the mean relative height between asperities increase. It decreases when the density of asperities increases. The aim of the study is to assess the origin of these correlations by means of the multi-asperity tyre/road contact model developed by the authors. For this purpose a number of artificial road surfaces composed of academic asperities of simple shapes (spherical, conical or cylindrical) are generated. The dynamical contact forces are calculated over several loops for a slick tyre rolling at different speeds. The spectra for a periodic road surface clearly show that the excitation frequency of the tyre within the contact area is directly due to the speed and the distance between asperity tips in the rolling direction. For randomly distributed artificial surfaces, broad band spectra are obtained with a cut off frequency linked to distance between successive contacts in the rolling direction while the mean relative height has few influence. The results are discussed and compared with spectra of contact stresses for real road surfaces within the framework of tyre/road noise.
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