We discuss the parallel performances of discontinuous Galerkin solvers designed on unstructured tetrahedral meshes for the calculation of three-dimensional heterogeneous electromagnetic and aeroacoustic wave propagation problems. An explicit leap-frog time-scheme along with centered numerical fluxes are used in the proposed discontinuous Galerkin time-domain (DGTD) methods. The schemes introduced are genuinely non-dissipative, in order to achieve a discrete equivalent of the energy conservation. Parallelization of these schemes is based on a standard strategy that combines mesh partitioning and a message passing programming model. The resulting parallel solvers are applied and evaluated on several large-scale, homogeneous and heterogeneous, wave propagation problems.