The development of the different sound packages in vehicles (dash/floor silencer, headliner, door trims…) is often driven mainly by high-frequency, airborne considerations. Nevertheless, those parts can have a considerable impact to acoustic performance at much lower frequencies, and their effect is not limited to airborne phenomena. As such, a proper consideration of their performance is very important when developing typical mid-frequency performances such as engine and road noise.This paper outlines a process that allows development of the vehicle body, and more specifically the sound packages, for mid-frequency acoustic performance. Two main challenges are addressed: first, full-vehicle targets have to be cascaded down towards specific sound package targets. It is shown that an effective cascading process can be set up based on Transfer Path Analysis (TPA) and Panel Contribution Analysis (PCA) techniques. A point of attention is the selection of suitable metrics to use in the cascade, in particular for characterization of the sound package performance.The second challenge is the development of sound packages for mid-frequency performance (including structure-borne excitation). The key ingredient of the proposed solution is a design space exploration framework, mapping silencer performance to typical design parameters (e.g. mass, package space, material properties). The resulting performance maps can be used to support the development of sound packages throughout the different vehicle development phases.