Aerospace structures are often subjected to a broad spectrum of mechanical and/or aerodynamic excitations and, therefore, there is a real need for the development of a modeling technique which can be used for the vibroacoustic analysis, with high fidelity and adequate spatial and spectral resolutions, of complex systems over the entire frequency range. A dynamic system typically exhibits distinctively different response characteristics as frequency increases. In recognizing the complicated behavior of a structure, the modeling methods in dynamic analysis are usually classified into low, mid, and high frequency models. A substructure-based modeling technique, based on enhanced Fourier Spectral Element Method (FSEM), that is applicable all frequencies, is proposed for the modeling of complex dynamic systems. This method also does not require meshing as is traditionally used in discretization methods such as finite and boundary element methods.