A device for reducing the jet noise of a turbomachine, the turbomachine having a longitudinal axis and a substantially cylindrical nozzle extending along the longitudinal axis of the turbomachine, having a downstream end for mixing the flows of gas inside and outside the nozzle, the device comprising a plurality of corrugations disposed to extend the downstream end of the nozzle, and a plurality of notches disposed between pairs of successive corrugations in the plurality of corrugations, and the plurality of corrugations and the plurality of notches are symmetrical relative to at least one axis perpendicular to the longitudinal axis of the turbomachine so as to generate a dual counter-rotating effect between the gas flows.