A jet engine includes a hollow nacelle including a front air intake section and a rear air outlet section having outer and inner annular surfaces which converge to form a trailing edge. A fan opposite the front air intake section to generate a cold stream. A generator downstream of the fan, to generate an axial hot stream. A cowl system including a rear section with outer and inner annular surfaces which converge to form an outlet orifice for the hot stream. The trailing edge of the nacelle forms the outlet orifice for the cold stream. Blind notches attenuate the jet noise at the periphery of the outlet orifice for at least one of the streams. The notches cut into one of the convergent annular surfaces forming the outlet orifice without cutting into the other of the convergent annular surfaces.