For the purpose of this report vehicle noise is considered to consist of two parts, power train noise and rolling noise. Vehicles are classified by total noise into two groups and simplified descriptions of vehicle noise as a function of speed are presented. Estimates of rolling noise are compared with the vehicle noise relation. It is shown that rolling noise is the dominant noise source for light vehicles travelling in top gear, and that it makes a measurable contribution both to the noise made by heavy vehicles when travelling in top gear and to the noise of light vehicles under urban conditions. Rolling noise is shown to limit the possibilities for developing quiet vehicles. Rolling noise has been the subject of a number of experimental studies and these are briefly reviewed. However as yet no completely satisfactory description of the mechanisms of rolling noise has been reported. An experimental investigation at the transport and road research laboratory has shown that for UK vehicles operating over typical UK road surfaces the major parameters of rolling noise are vehicle speed, whether the road is wet or dry, tyre tread pattern and road surface type. A comparison of braking force coefficients with rolling noise levels indicate that it is not necessarily true that reducing tyre noise must reduce adhesion. (Author/publisher)
Samenvatting