A feedforward control algorithm using a rpm reference signal and a rotor position signal was used to apply active noise control to reduce the far-field noise generated by a ducted propeller. This technique reduced the noise radiated from the plane wave and first circumferential (1, 0) spinning duct mode. Simultaneous cancellation of the blade passing frequency and the first harmonic was achieved. These reductions were obtained over a wide range of far-field angles with no increase in noise at other frequencies. Mmeasurements show that digital feedforward active common using input from a blade position sensor is a simple and very effective approach to attenuate tones from a ducted propeller system. No on-line error microphone is required with this method. The BPF and its harmonics can be simultaneously controlled as well as spinning modes. This work has shown effective control of the (1, 0) mode and the plane wave (0, 0) mode. Noise reduction is realized with this technique over a wide range of far-field angles without an increase in the SPL at other angular locations. It is also note worthy that the SPL doces not increase at other frequencies. The update time with this technique is small compared to other methods, and the results are effective in yielding reductions near the noise floor as defined by the broadband level. The method used in this study utilizes available knowledge about fan noise propagation in ducts, including well-documented information on spinnng modes. Use of this known information permits an effective ANC system with a very simple computational scheme that may be run on an extremely modest computer. In addition, the system identification need not be repeated at each start up.
Active control of far-field noise from a ducted propeller
Aktive Unterdrückung der von ummantelten Propellern verursachten Ferngeräusche
AIAA Journal ; 33 , 2 ; 231-236
1995
6 Seiten, 11 Bilder, 1 Tabelle, 10 Quellen
Article (Journal)
English
Active Control of Far-Field Noise from a Ducted Propeller
Online Contents | 1995
|Small aircraft propeller noise with ducted propeller
AIAA | 1998
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