In a series of Large Eddy Simulations with different forcing, we study thegeneration of internal gravity waves at the base of the surface mixed layer.If turbulent eddies act as obstacles and undulate the base of the mixed layer,horizontal velocities associated with inertial oscillations and Ekman dynam-ics can move the obstacles relative to the stratified interior exciting internalgravity waves similar to lee waves. We find strong evidence that the ’obsta-cle mechanism’ is able to excite large parts of the internal wave spectrumincluding near inertial waves. The high frequency part of the excited wavespectrum is filtered by the increased stratification in the transition layer be-tween the mixed layer and lower stratified interior but a substantial part of thewave spectrum is able to overcome this barrier hence contributing to interiormixing. The magnitude of the downward radiated energy below the transi-tion layer depends on the source of turbulence, but we show that the ’obstaclemechanism’, especially under destabilizing heat fluxes, has the potential tocontribute considerably to the internal wave energy in the interior ocean.