M. Kallergis

It is the purpose of this paper to show that attenuation of the farfield-radiated noise of aircraft-propellers is attainable by a superposition with the exhaust noise of the (piston-) engine. The feasibility of such "active noise control" (ANC) is demonstrated through ground-based and fly-over experiments. In correspondence to the classical ANC-method the principle applied here is to reduce the noise radiated.from a primary source (propeller) by superimposing a signal from a secondary source (engine exhaust), which is shifted in an anti-phase position to the primary sound signal. Within ground-stationary tests it could be shown that for a typical GA-type single engine propeller-driven aeroplane differences in the overall sound pressure levels of up to 5 dB were obtained between an "random" and an exact anti-phase superposition of the sound waves from the propeller and the engine exhaust. It was observed that - in fact - the sound pressure levels of the first nine harmonics of the blade passage frequency were reduced. Additional fly-over experiments yielded differences on the ground ranging from 4 to 6 dB between optimum and "random" relative positions of the crank-shaft and the propeller.

DGLR/AIAA 14th Aeroacoustics Conference, 1992

Conference Paper

englisch

21,0 x 29,7 cm, 12 Seiten

DGLR-Bericht, 1992, 1992-03, DGLR/AIAA 14th Aeroacoustics Conference - Proceedings; S.907-918; 1992; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn

NA

aeroacoustics, propellers

Bibliothek

1992