Acoustic Signature Reduction of Special Operations Forces Aircraft Using Flow-Excited Cancellation Sources

KCF Technologies in partnership with Lockheed Martin, Inc. proposes a lightweight, low drag, quasi-active noise control system to reduce the acoustic signatures of existing SOF fixed wing aircraft. The proposed solution is based on integrating flow-excited resonators near the blade tips of the propeller, commonly the aircrafts major noise source. The resonators are tuned actively to generate anti-phase, secondary sound, thereby cancelling the original blade tones and their harmonics. The resonators are positioned near the blade tips to produce dipole sounds that cancel those produced by the rotating propeller. This noise-cancelling mechanism is accomplished by tuning the resonators impedance and selective positioning of the resonators mouth with respect to the passing propeller blade tips. The proposed design will reduce the acoustic emissions of current SOF aircraft without significantly impacting vehicle performance. The design of the proposed solution, i.e., flow-excited resonant cavities, is inherently rugged, compact, lightweight and removable if required.