Frequency reduction and attenuation of the tire air cavity mode due to a porous lining

The tire air cavity mode is known to be a significant source of vehicle structure- borne road noise near 200 Hz for current generation passenger vehicles, and a porous lining placed on the inner surface of a tire has proven to be an effective countermeasure. The two noticeable effects of such a lining are the reduction in the cavity resonance frequency and the attenuation of the air cavity mode. In the present work, through both theoretical and numerical analysis, the mechanisms underlying the effects of a porous lining were studied. A two-dimensional duct-shaped theoretical model and a two-dimensional torus-shaped numerical model were created to investigate the lined tire in conjunction with the Johnson- Champoux-Allard model describing the viscous and thermal dissipative effects of the porous material. The design parameters of the porous lining were varied to study their impact and to identify optimal ranges of the design parameters, in particular, the flow resistivity. Finally, in an experimental analysis, the sound attenuation and the frequency drop were observed in measurements of force, acceleration, and sound pressure. In conclusion, it was demonstrated that the suggested theoretical and numerical models successfully predict the effects of porous linings and that the frequency reduction results from the decreased sound speed within the tire owing to the presence of the liner.