Experimental investigation of road surface parameters affecting tire/road noise

It is known that tire/road noise is strongly affected by the properties of the road surface such as its profile and sound absorption coefficient. Several parameters, represented by mean profile depth (MPD), have been proposed or standardized as surface profile parameters, but none of them clearly explains the relationship with tire/road noise generation. This study attempted to identify a new surface parameter that correlates more closely with tire/road noise. Surface profile measurements and close proximity (CPX) measurements were conducted on several road surfaces with different properties on test tracks. Tire P1, the reference tire for the CPX method, and two types of passenger car tires were used for the CPX measurements. According to our experience, the variation of the peak height of the road surface with distance is closely related to the excitation input to the tires and thus noise generation. Therefore, we devised a road profile parameter to quantitatively evaluate the variation of peak height. A relatively strong correlation was observed between this parameter and the CPX level. The validity of this parameter will be verified by further measurements on general roads in the future.