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In this research, the influence of tire size and shape on sound radiation in the mid-frequency region was studied. First, the relationship between the structural wave propagation characteristics of a tire excited at one point and its sound radiation was identified by using FE and BE analyses. Then, by using that relationship, the effect of modifying a tire's aspect ratio, width and wheel diameter on its sound radiation between 300 Hz and 800 Hz was investigated. Finally, an optimization of the sound radiation was performed by modification of the tire structure and shape. It was found that most of a tire's structural vibration does not contribute to sound radiation. In particular, the effective radiation was found to occur at the frequencies where low wave number components of the longitudinal wave and the flexural wave first appear.

The damping effect that is observed when a fibrous acoustical treatment is applied to a thin metal panel typical of automotive structures has been modeled by using three independent techniques. In the first two methods the fibrous treatment was modeled by using the limp frame formulation proposed by Bolton et al., while the third method makes use of a general poro-elastic model based on the Biot theory. All three methods have been found to provide consistent predictions that are in excellent agreement with one another. An examination of the numerical results shows that the structural damping effect results primarily from the suppression of the nearfield acoustical motion within the fibrous treatment, that motion being closely coupled with the vibration of the base panel. The observed damping effect is similar in magnitude to that provided by constrained layer dampers having the same mass per unit area as the fibrous layer.

The objective here was to study the control of sound radiation resulting from the structural vibration of a tire excited at one point. First, the tire was modeled as an orthotropic shell by using finite elements and the effect of various tire material parameters on structural wave propagation and the associated sound radiation was estimated. The parameters that were effective at controlling structural wave propagation were then identified. In addition, the radiation field characteristics in the space surrounding a tire placed on a rigid ground were analyzed by using radiation mode analysis. Based on these analyses, a strategy for reducing the radiated sound levels by modifying the tire parameters from a base set was determined. An improved set of material parameters was identified that resulted in reduced sound radiation within a specified target frequency region.