Active Local Control of Propeller-Aircraft Run-Up Noise

Abstract

Engine run-ups are part of the regular maintenance schedule at airports. The noise generated by the run-ups propagates into neighbouring communities, disturbing the residents. Active noise control is a potentially cost-effective alternative to passive methods, such as enclosures. Propeller aircraft generate low-frequency tonal noise that is highly compatible with active control. This paper presents a preliminary investigation of the feasibility and effectiveness of controlling run up noise from propeller aircraft using local active control. Computer simulations for different configurations of multi-channel active-noise-control systems, aimed at reducing run-up noise in adjacent residential areas using a local-control strategy, were performed. The variations of the attenuation and amplification zones with the number of control channels, and with the source/control-system geometry, were studied. The aircraft was modeled using one or two sources, with monopole or multipole radiation patters. Both free-field and half-space conditions were considered, for the configurations studied, results were similar in the two cases. In both cases, large triangular quiet zones, with local attenuations of 10 dB or more, were obtained when nine or more control channels were used. Increases of noise were predicted outside of these areas, but these were minimized as more control channels were employed. By combining predicted attenuations with measured noise spectra, noise levels after implementation of an active control system were estimated.