Wind turbine design requirements are increasingly focussing on vibration and noise emission levels. In addition to the
rotor and blades also the drive train is a contributor to the overall noise and vibrational behaviour of the wind turbine.
Therefore good dynamic design of the drivetrain is highly important. With regard to acoustic radiation both excitations
at gearbox input and output as internal excitations originating from the gears are important. Two acoustic phenomena are
investigated: structure borne excitation past by/comming from the gearbox through the nacelle to the receiver and airborne
noise directly radiated from the gearbox housing. This work discusses the use of a flexible multibody in combination
with a Boundary Element Model (BEM) to asses these phenomena. The multibody model is used to calculate the housing
vibrations. A method is discussed to convert these deformations at the structural mesh nodes to the nodes of the BEM
mesh. Furthermore the contribution of the transmission error and the gear shuttling mechanisms in the level of structure
borne and airborne noise is shown.