A Review of Active Noise Control Strategies For Reduction of Rotorcraft Interior Noise

Source mechanisms and transmission paths of rotocraft interior noise are well defined. Rank ordering of these sources has established the main rotor gearbox as the primary contributor to the cabin noise levels. Gear-mesh vibrations generate a series of harmonic tones within the cabin, the most significant of which is typically the fundamental mesh tone at approximately 700-800 Hz. Current passive noise control methods (e. g. , the fuselage sidewall treatments) do not adequately reduce cabin noise levels to provide passenger comfort, especially for extended flights. Further sidewall treatments can add substantially to weight penalities and cost. Thus, new lightweight noise control methods are needed to reduce rotorcraft interior noise.