Abstract: Most of cabs on tractors and vehicles can be considered as combined plate structures. It is difficult to analyse and estimate the structure borne sound and the noise level inside them. A tractor cab here is modeled as a combined structure with seven plates. In accordance with the basic SEA theory, an expression for calculating vibrational power flow is derived, and the radiated noise from plates into the internal acoustical space is calculated. There is a good agreement between calculated and measured results. It is of much importance to the quantitative analysis of solid borne sound and noise prediction.