This study focus on the acoustical behavior of gearbox induced by the static transmission error under load (STE). An original method is developed allowing to compute simultaneously STE, meshing and bearings stiffnesses. These characteristics mainly govern the vibrational and the acoustical behaviors of the geared system. The proposed procedure is based on two computational methods allowing to calculate the STE and the bearing equilibrium which are integrated in a coupled computational procedure. The technique has been implemented to treat an illustrating example and compared to standard uncoupled approach. Comparative results concern the STE, meshing stiffness, bearings stiffnesses, shafts misalignments, critical eigenmodes and associated critical running speeds, housing vibratory response and radiated noise.