The electrification of vehicle propulsion has changed the landscape of vehicle NVH. Pure electric vehicles (EV) are almost always quieter than those powered by internal combustion engines. However, one of the key challenges with the development of range extended electric vehicles (ReEV) is the NVH behavior of the vehicle. Specifically, the transition from the EV mode to one where the range extender engine is operational can cause significant NVH issues. In addition, the operation of the range extender engine relative to various driving conditions can also pose significant NVH concerns.In this paper internal combustion engines are examined in terms of their acoustic behavior when used as range extenders. This is done by simulating the vibrations at the engine mounting positions as well as the intake and exhaust orifice noise. By using a transfer path synthesis, interior noise components of the range extenders are calculated from these excitations. The results from this study show a few promising internal combustion engines concepts such as the inline-six-cylinder engine, the single-rotor Wankel engine, and the two-cylinder-boxer engine in combination with a neutral torque axis mounting. When using other mounting positions, an internal rolling moment compensation system is shown to reduce the engine vibrations and hence the interior noise.