An analysis of tire radiation properties using dispersion diagrams

Road traffic noise created by tire/road interaction not only depends on the road surface properties and the tire tread pattern geometry, but also on the tire construction. Besides the footprint shape, the tire construction can also affect the radiation efficiency of the tire modes. Dispersion diagrams represent the circumferential mode number of a mode shape as a function of its natural frequency. Identification of key branches in the dispersion diagram for a tire can help in understanding tire noise radiation under working conditions. After performing a cluster analysis, where all points belonging to the same branch associated with a particular cross sectional mode shape deformation are identified, differences in tire specification are considered, and their respective dispersion diagrams are compared. First results reveal that by changing the tire stiffness (e.g. by increasing belt angle or inflation pressure) the shape and slope of the different branches are changing. Which branches remain unchanged, and which are most sensitive to these changes can reveal how differences in tire structural composition influence the modal wavelength and consequently the radiation efficiency of the different modes.