Active aircraft cabin noise control via loudspeakers

The relatively high noise levels in turboprop aircraft cabins may be very unpleasant for both passengers and pilots. The noise power is radiated from the propeller blades into the cabin by the vibrations of the fuselage structure. It exhibits a mainly tonal nature, with low frequency characteristics. Unfortunately, traditional passive approaches for acoustic attenuation are limited in their low frequency effectiveness by weight and space constraints, especially for lightweight propeller aircraft. On the other hand, active control offers an attractive approach for low frequency acoustic noise attenuation inside the aircraft cabin. Several techniques are under investigation to evaluate the possibility of reducing the noise in the aircraft cabin by active noise control strategies that may provide more efficient, lightweight and relatively cheap solutions. Among others, a possible approach consists of using concentrated acoustic waves generators (loudspeakers) located inside the cabin, in order to produce a more acceptable resultant acoustic field. In this paper, an active noise-control technique has been developed for the control of the interior noise level in an aircraft cabin. Noise reduction is achieved by driving an array of speakers located over the surface of the radiating structure. A procedure of optimal allocation of such loudspeakers is also proposed in order to obtain optimal results in terms of noise reduction in predefined regions of interest.