O. Bschorr

The aim of this paper is to assess the possibilities of the anti-noise technique for reducing propeller noise. Therefore a mathematical model was established to simulate the propeller noise and the anti-noise. With this model the noise foot prints of a propeller engine with and without anti-noise was calculated for the two main components, the blade-thickness noise and the thrust noise. Using a single anti-noise source it is possible to reduce the peak level more than 10 dB, but away from the optimum cancellation direction and for the higher harmonics the superposition causes an amplification. This effect can be avoided by changing the cancellation direction and also by reducing the acoustic power of the anti-noise source. With an anti-noise power of only 25 % of the propeller noise one obtains a noise reduction of about 5 dB within a cone of 45°. - Using two or more antinoise sources the cancellation region can be enlarged, up to an omnidirectional noise reduction. Because of the size and the low efficiency electromagnetic loudspeakers are unsuf f icient as anti-noise source. More suitable are pneumatic driven sirens. In laboratory tests the theoretical values are confirmed experimentally.

DGLR/AIAA 14th Aeroacoustics Conference, 1992

Conference Paper

englisch

21,0 x 29,7 cm, 10 Seiten

DGLR-Bericht, 1992, 1992-03, DGLR/AIAA 14th Aeroacoustics Conference - Proceedings; S.919-928; 1992; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn

NA

aeroacoustics, propellers

Bibliothek

1992