Point excitation of a coupled structural-acoustical tire model with experimental verification: Higher order cavity modes

The acoustical modes that exist within a tire's interior cavity have an important influence on tire-road noise, particularly structure-borne noise. The first circumferential mode is most commonly considered: it occurs when the average circumference of the tire interior cavity is approximately one wavelength. However, that mode is just the first of a family of circumferential and radial modes, the latter of which, in particular, are rarely considered, but which were the primary focus here. A modal expansion method was utilized to solve for the point excitation of a fully-coupled, ring-like structural-acoustical tire model. From that model, the dispersion features associated with the radial acoustical modes, which typically first appear between 1400 and 2000 Hz depending on the tire geometry, were identified, and their existence was verified by making detailed measurements on tires. The surface radial velocity of the tire was measured using a laser Doppler velocimeter (LDV), and a point-by-point measurement method was proposed to minimize the measurement error that can occur due to the tangential motion of the treadband.