Acoustic noise reduction for large aircraft

The feasibility of applying the following five in-house innovative active noise control technologies to suppress turbofan and turboprop engine noise will be investigated: (1) the design of a hybrid active/passive compact active control system, to reducetonal and broadband noise radiated by rotor/stator interaction in turbofan engines, (2) the design of an active control system to reduce aircraft turbofan engine inlet/exhaust tone noise generated when rotor tip speeds become transonic, (3) to assess thefeasibility of installing vane-mounted microphones for reference signal acquisition and quasi-near field duct-wall mounted actuators for anti-sound injection to suppress broadband rotor/stator noise,. (4) to develop active control double degree of freedomacoustic liners and (5) to assess the feasibility of installing active transducers to cancel radiated noise in specified directions to reduce noise footprint area. Development of a feasibile active control strategy to suppress excessive engine noisegenrated from naval aircraft offers the opportunity to meet the Navy's target goals to reduce source aircraft noise levels by more than 20dB.