US Patent 10371170 Noise reduction using IGV flow ejections

In one embodiment, a method for reducing noise generated by inlet guide vane (IGV) wake and rotor interaction in a turbine engine, the noise having acoustic energy substantially dominating at one or two frequencies, comprises altering noise frequencies to distribute the acoustic energy into a broadband frequency spectrum by ejecting fluid flows from holes located on a side near a trailing edge of at least one of a plurality of inlet guide vanes (IGVs), toward a rotor downstream of the IGVs to merge with an air flow guided by the side of the at least one of the IGVs for interfering with said IGV wake and rotor interaction.