Automotive tyre cavity noise modelling and reduction

Noise and vibration in automotive vehicles relates to a feeling of luxury. Noise, Vibration and Harshness engineers spend significant time tuning designs to achieve this. Low noise must be achieved against a requirement to reduce weight, installation time, manufacturing complexity, achieve a carbon reduction and an increase in fuel economy.One particularly annoying noise originates in the pressurised air cavity bounded by the metal wheel and tyre rubber surfaces and is referred to as "tyre cavity noise". It is a particularly problematic resonance due to the low frequency (approximately 200 - 250Hz) and the low loss factor of air, causing high amplitude sound. Traditionally, this is addressed through the careful choice of suspension natural frequencies to avoid coupling resonances and addition of mass damping layers to the cabin and transmission paths.In this paper, a numerical model of the tyre cavity is produced with passive resonators to reduce the noise. Complications that arise due to wheel loading, speed, temperature changes and manufacturing durability are discussed, with a optimisation routine used to obtain tuned Helmholtz resonators for inclusion in wheel spokes. A stationary experimental rig is introduced as a validation tool, with an array of microphones used to illustrate mode shapes.