Analyses of correlations between tyre noise and road texture are made on the basis of measured tyre noise frequency spectra for a passenger car tyre and a truck tyre rolling on three road surfaces, as well as frequency spectra of the longitudinal surface profile curves for the corresponding road surfaces. The differential frequency spectra for noise and surface texture are compared. As there is a distinct correlation between these differential spectra for one pair of road surfaces it is concluded that road texture induced tyre vibrations are the dominating generation mechanism. Calculations of the frequency response function for the tyre with respect to road texture are made. The calculations indicate that passenger car tyres are sensitive to road texture in the region 125-1000 Hz, corresponding to road irregularity wavelengths of 160-20 mm. The truck tyre appears to be approximately as sensitive to road texture as the passenger car tyre provided the differences in contact area are compensated. A theoretical discussion of the possibility to clearly detect a frequency shift due to speed for road texture induced noise, is showing that this would be possible only for a periodically grooved pavement and a smooth patterned tyre. The results are supporting the suggestion that a tyre - with respect to road texture induced noise - can be considered as a filter; consequently the noise emission could be partly explained by this filter model.
Abstract