Modeling of Airborne Tire Noise Transmission into Car Interior by Using the Vibro-acoustic Reciprocity and the Boundary Element Method

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. Acoustic pressure distribution over the exterior car panels can thus be predicted and the contribution of local vibrational velocity of tire wall to car panels are estimated by the vectorial summation of resultant acoustic pressures. Second, vibro-acoustic transfer functions between the various points of car panels and the receiver's ear position in the car interior is measured by utilizing the vibro-acoustic reciprocity principle. Combining these two transmission path models in series, the airborne noise transmission from tire wall vibration to driver's ear can be analyzed. From the results, contributions of tire wall vibration to the interior noise can be estimated and the main possible transmission paths of airborne tire noise can be identified.