Nonlinear finite element analysis has been applied to determine the conditions conducive to seal system aspiration. Aspiration noise occurs and propagates into the passenger compartment of a vehicle when there exists a gap between the seal and sealing surface due to pressure differential between the vehicle interior and exterior. This pressure differential is created by the vehicle movement which reduces the pressure acting on the exterior surface of the vehicle, and it is on the order of , where ρ and U∞ are the density of air and vehicle speed, respectively. The pressure difference is also created by turning on the climate control system which pressurizes the passenger cavity. Since aspiration increases door seal cavity noise level and creates a direct noise transmission path without any significant transmission loss, the presence of an aspiration noise source can dominate the vehicle interior noise level if it is close to the driver or passenger's ears. Thus, one of the most important factors in reducing vehicle interior noise level is to prevent door and glassrun seal aspiration. This paper explains how to predict and therefore how to prevent aspiration noise. Using this analysis procedure, we determine the effect on aspiration of such parameters as initial seal height, seal shape, seal thickness, seal constitutive model, friction, and seal compression due to door closing. This analysis tool has been applied to production vehicles in order to determine the aspiration characteristics of glassrun seal systems.