Wave propagation in tyres and the resultant noise radiation

Tyre noise has become an increasingly important road traffic noise source. This is because other sources on the vehicle, such as the air intake system, the exhaust system and the engine, have tended to become relatively quieter. This situation forces the tyre noise component to be reduced in order to achieve a reduction in the overall traffic noise level.In the research reported here, vibration, sound radiation and sound transmission of a passenger car radial tyre were investigated. The first half of this thesis discusses the vibration characteristics using two methods: (1) FEM to analyse tyre modal behaviour in detail, (2) Analytical models to interpret the FEM results. These models have both advantages and disadvantages in investigating tyre vibration. Combining the two methods is necessary in order to fully understand the vibration behaviour of a tyre. Dispersion relationships and the related frequency of tyre modes are analysed by FEM and the flexural wave propagation in the tyre shell, and the sound radiation of the tyre wall by flexural modes is analyzed using plate and shell theory.The second part of this thesis discusses the radiation and transmission of tyre noise. To predict the radiation of sound with only a knowledge of the surface vibration velocity, the experimental Green's functions were estimated by using the acoustic reciprocity principle. This technique was also applied to separate airborne noise from structure borne noise for identification of the transmission path of tyre noise into a vehicle cabin and quantification of the relative contribution of various regions of the vibrating tyre surface to vehicle interior noise. The application of acoustic reciprocity for the tyre noise problem was verified and compared with BFM analysis.