US Patent 10024236 Acoustically optimized air inlet

A nacelle structure (10) surrounding a fan, the structure comprising an air inlet (100) having an inside surface (100A) defining an air feed channel; and at least one ring (22) arranged in the air inlet and selectively movable between a deployed position in which the ring is moved radially inwards from the inside surface to provide an obstacle to shock waves coming from the fan, and a retracted position in which the ring is moved radially outwards from the deployed position so as to become flush with the inside surface and thus reconstitute the air feed channel.