An engine and a generator driven by the engine are resiliently supported on a frame. A duct member is integrally attached to the engine and the generator to define a continuous cooling-air passage between the duct member and outer peripheral surfaces of the engine and the generator. A cooling fan is disposed on an inlet side of the cooling-air passage. A silencing plate is integrally attached to the duct member and faces an inlet of the cooling-air passage with a ventilation gap defined therebetween. The silencing plate has an area opposing the inlet that is larger than an opening area of the inlet.