Impact of the contact-patch gap on sound radiation from a tyre

Abstract

Depending on location, vibrations on a rolling tyre may vary significantly in the noise they produce. Calculation of their amplification is thus central to tyre-noise prediction. However, the appropriate representation of sound propagation through the contact-patch region remains uncertain. More fundamentally, it is not even known whether this aspect is important. Here, this question is investigated via Boundary Element Method calculations for an idealised geometry, in which the irregular gap in the contact patch is represented by a constant-height channel between the road and the flattened-off portion of a cylinder. Compared to calculations with no gap, the results show attenuation of the high amplification levels in the horn-like region where the tyre nears the road, and introduction of source amplification within the gap. These features are evident for a gap as small as 1% of the cylinder radius (approximately 3 mm for a representative tyre). On this basis, it appears that the contact-patch region must indeed be modelled, and that parts of the tyre other than the horn may be significant contributors to the radiated noise.