Active control of aircraft engine inlet noise using compact sound sources and distributed error sensors

Abstract

An active noise control system using a compact sound source is effective to reduce aircraft engine duct noise. The fan noise from a turbofan engine is controlled using an adaptive filtered-x algorithm. Single, multi channel control systems are used to control the fan blade passage frequency (BPF) tone and the BPF tone and the first harmonic of the BPF tone for a plane wave excitation. The multi channel control system is used to control fan tones and a high pressure compressor BPF tone simultaneously, and any spinning mode. A compact sound source is employed to generate the control field. This compact sound source consists of an array of identical thin, cylindrically curved panels (125) with an inner radius of curvature corresponding to that of the engine inlet. These panels are flush mounted inside the inlet duct (Inlet Wall) and sealed on all edges to prevent leakage around the panel.