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Active control of run-up noise from propeller aircraft Germain, Pierre

Abstract

Engine run-ups are part of the regular maintenance schedule at Vancouver Airport. The noise generated by the run-ups propagates into neighbouring communities, disturbing the residents. This research focuses on controlling run-up noise from propeller aircraft. It is well known that passive control measures - such as aircraft enclosures and acoustic barriers - can only attenuate sound at high and mid frequencies. Conversely, Active Noise Control (ANC) a new technology involving using noise to reduce noise, is an inexpensive alternative to enclosures. Propeller aircraft generate tonal noise that is highly compatible with ANC . Tests on a Beechcraft 1900D found that the fundamental frequency of 112 Hz, as well as the first three harmonics, generated high noise levels in a community 3 km away from the run-up site. The insertion loss of an existing blast fence at the run-up site was measured, and found only to be efficient above 200 Hz. Computer simulations for different arrangements of ANC systems aimed at reducing run-up noise in residential areas were performed. Large triangular zones of local attenuation of 10 dB or more were obtained when 9 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. Using an ANC system in conjunction with a barrier, such as the existing blast fence, was shown to provide attenuation at all frequencies. ANC experiments were conducted in an anechoic chamber using 1 and 3 control channels. The fundamental and first harmonic of the Beechcraft 1900D noise were significantly attenuated with ANC. The experimental data correlated well with the theoretical predictions, validating the simulations. The results from both the computer simulations and experiments indicated the great potential of controlling run-up noise with multi-channel ANC systems. However, implementing a real ANC system at Vancouver Airport would require further evaluating the required size o f the quiet zone as well as selecting the number of control sources and the distance from the primary source to the control sources accordingly.

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