A Study on Tire-Structure-Borne Sound

Abstract

A set of theoretical models has been prepared which describes the noise generated by tire/road interaction. The mechanisms are considered to be air pumping and carcass vibration. The models begin with a set of thin shell equations describing the motion of the belt of a radial ply tire, as derived by Böhm. The structural quantities required for these equations are derived from the material properties of the tire. The rolling shape of a tire is computed from the steady-state limit of these equations. Air pumping (monopole radiation from head voids) is calculated by assuming that tread elements move passively on the deformed tire. The vibration response of the tire is treated using full time-dependent shell equations. The force input at the tire/road interface is calculated on the basis of tread geometry and the distribution of contact patch pressure. This input is physically equivalent to the impulse distribution models widely used in the tire industry for tread pitch randomization. The subsequent radiation of sound is calculated by a Raleigh integral. These models have been embodied into a unified set of computer programs. Using the programs, the effect on noise of various tire design variations is determined and discussed. Trends that lead to low-noise design are identified. A series of experiments are planned which will test the validity of the models and provide a basis for their refinement before final documentation and dissemination.