Patent ID: 8033358

Claim:
An aircraft engine, said aircraft engine having a takeoff speed and a landing speed, said aircraft engine including a duct with at least a first acoustic control noise reduction tube, said tube having a tube path between a tube entrance end and a distal tube exit end, said tube having a nonobstructive frequency f no , said tube containing a movable frequency tuner obstruction, said movable frequency tuner obstruction movable along said tube path between a first takeoff frequency obstruction tube path location with a first tube cross-section area, and an at least second landing frequency obstruction tube path location with a second tube cross-section area, said frequency tuner obstruction positioned at said first takeoff frequency location with said takeoff speed, said frequency tuner obstruction positioned at said second landing frequency location with said landing speed with said frequency tuner obstruction having a tuner obstruction cross-section area wherein said tuner obstruction cross-section area is no greater than 99% of said first tube cross-section area and said tuner obstruction cross-section area is no greater than 99% of said second tube cross-section area.