A finite element-based acoustic-structure interaction modeling procedure is developed to determine the sound transmission loss characteristics of automotive door seals. The model accounts for the effects of seal system compression, the density and constitutive behavior of the materials used in the seal construction, individual seal cross-sectional geometry, and spacing between layers of seals. The results of a sensitivity analysis conducted using the modeling procedure reveals that the overall transmission loss of door seal systems is most sensitive to changes in: seal material density, geometry of the seal in the compressed deformed configuration, and geometry of the cavities formed by the space between seals of adjoining layers. An important implication arising from the sensitivity analysis for the design of door systems for closing efforts is that, without changing seal system compression load deflection behavior, the sound transmission characteristics may be altered substantially by changing the spacing between layers of seals in the system. The results of the sensitivity study and an application to a prototype door seal system demonstrate that the new modeling procedure can be used to effectively eliminate much of the ``cut and try'' from the present process of designing door seal systems.