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Sound transmission into a vehicle is classified as either airborne of structure-borne sound. From the point of view of noise control, the reduction of noise transferred by different paths requires different solutions. Coherence function analysis is often used to identify transmission paths. However it can be difficult to separate the airborne from structure-borne components. The principle of acoustic reciprocity offers a convenient method for overcoming this difficulty. The principle states that the transfer function between an acoustic volume velocity source and an acoustic receiver is independent of a reversal of the position of source and receiver. The work done on this study involves exciting a stationary tire and measuring the surface velocity of the tire at a number of discrete points. The acoustic transfer functions between each point on the tire and a receiver point are measured reciprocally.

In this paper, the vibro-acoustic transmission characteristics are investigated in the view point of the airborne noise in the interior cavity due to the tire wall vibrations. The analysis is carried out by categorizing the airborne noise transfer path into the two separate consecutive events. First, the noise transfer from the vibrating tire wall to the exterior car panels is modeled by using the direct boundary element method (BEM). To this end, after discretizing the whole geometry of exterior body panels, tires, and ground into BEM models, vibro-acoustic transfer characteristics are investigated at several frequency components associated with the cavity resonances of tire. Here, cavity resonance frequencies of tire are estimated by BEM and the distribution of tire wall vibrations excited by a special vibro-acoustic source is measured at those frequencies.