Experience of the National Aviation University in the application of active noise control in an aircraft cabin

Abstract

This presentation is focused on the problem of noise reduction in the aircraft cabins including cockpits. The noise has an adverse effect on the crew first of all, since it is disturbing, tiring, and interferes with transfer and recognition of information. Together with other adverse factors it can result in human errors and hence influence on flight safety. Aircraft cabin noise can be generated by a variety of sound sources. The main of them in aircraft cabins include: the power unit (engines), the turbulent boundary layer on aircraft surfaces, the avionics, and the air conditioning system (ACS). The noise from power unit, turbulent boundary layer is transmitted through the fuselage. The structural-born noise is also one of essential sources of noise in aircraft cabin. Spectrum of the noise in the cabin is broadband with tonal components. There are two major techniques for reducing noise: passive and active. Passive noise control is based on the absorption and/or reflection properties of materials, and is effective for high-frequency noises. However, these passive techniques are not effective at low frequencies. The most effective way to reduce of cabin noise in low frequency range is to use active noise control (ANC) system. ANC is based on the principle of superposition, where the secondary loudspeaker generates an anti-noise with the same amplitude but an opposite phase in order to cancel the primary noise produced by the noise source. Feedforward and feedback control are the two main methods that have been used for ANC system. A feedforward controller requires a measure of the incoming disturbance to generate the required control signal for the control source. A feedback controller requires no knowledge of the incoming disturbance and acts to change the system response by changing the system resonance frequencies and damping. […]