UBC Theses and Dissertations
Active control of propeller aircraft run-up noise Nakashima, Ann Marie
In 2000, the first phase of research on the feasibility of using active noise control (ANC) to control the noise from propeller aircraft run-up tests was completed by Germain. ANC is a noise cancellation technique that has been the focus of much research in recent years. It was of interest to extend the work by Germain, concentrating on the effects that phenomena such as atmospheric refraction and the ground impedance have on the performance of an ANC system. Furthermore, since propeller aircraft were found to have directional noise radiation, the studies must consider the effectiveness of an ANC system on complex noise sources. The effectiveness of an ANC system on a dipole noise source was investigated in a free-field environment through simulations and experiments. It was found that the performance of an ANC system depends on the orientation of the dipole noise source, and that the system is most effective when used to control noise in the direction of the strongest radiation of the source. Measurements of run-up noise from a Dash-8 were taken and analyzed to gain a better understanding of how it acts as a noise source. It was found that the full-power engine noise is strongly tonal, making it a possible candidate for ANC. The noise was also found to be strongly directional. The Green's function parabolic equation (GFPE) method for outdoor sound propagation was modified to include a single active control channel, and ANC predictions were performed in the case of reflective and soft grounds for different atmospheric conditions. The preliminary results show that atmospheric refraction causes fluctuations in the noise attenuation achieved by a single-channel control system, and has the overall effect of decreasing its performance. It is evident that multiple control channels must be used in order to achieve significant attenuation for realistic outdoor conditions. Further research is required to determine if multi-channel ANC is a realistic method for the control of propeller aircraft run-up noise in realistic situations.
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