Patent ID: 6896100

Claim:
A noise reducing apparatus for a jet engine comprising: a mixer to mix exhaust gas from the engine and external air; a flowing channel forming section, which forms a flow channel that accelerates the exhaust toward the mixer in a noise reducing mode and a flow channel that introduces external air to the mixer, wherein noise due to exhaust gas from the engine is reduced in the noise reducing mode, and wherein the flow channels have a circular cross-section and wherein a flow channel comprises: a first movable member which is part of a duct facing external air in a cruising mode and which guides the external air diagonally from the duct to the mixer in the noise reducing mode; a plurality of second moveable members which are disposed apart from each other in a cruising mode and contact each other in the noise reducing mode and form a diaphragm flow channel thereinside; an actuator which changes disposition of the first and second moveable members according to the mode.