We consider the simulation of elastodynamic waves in layered structures with piecewise constant isotropic material parameters and horizontal translational symmetry. The governing equations are discretized on a planar triangular mesh using discrete exterior calculus (DEC) with periodic and absorbing boundary conditions modelling the infinite domain. The structure is illuminated with plane waves at varying frequencies, angles of incidence, and polarizations, measuring outgoing energy to obtain transmission coefficients for the corresponding phonon modes. Results can be applied e.g. to the estimation of heat conductivity in low-temperature nanostructures. The simulations are implemented and visualized using our open-source Rust library dexterior, which is also briefly introduced in the presentation.