Local active noise attenuation in a small piston engine aircraft cabin

Abstract

Most cases of global active noise reduction in commuter turboprop aircraft cabins have been attempted at low frequencies. The case of noise reduction applications for a smaller piston engine aircraft has been studied less, although they are noisier than turboprops with levels of up to 100 dBA. Specifically, the case of a six-seat, two-engine aircraft is studied here for an active noise control application. The main frequencies for noise reduction have been found at BFP (75 Hz) and some harmonics, 225 and 375 Hz (according to A-weighted noise levels). Computer model analysis of the cabin shows that only the peak at 75 Hz could be globally controlled, so the local control strategy is selected for application. Zones of attenuation around the head of a hypothetical passenger and attenuation at their ear, applying local control strategy, are obtained for different configurations in laboratory and eventually tested under flight conditions.