Experimental and analytical studies of shielding concepts for point sources and jet noise
Abstract
Concepts for jet noise shielding were explored. Model experiments center on solid planar shields, simulating engine-over-wing installations and sugar scoop shields. Tradeoff on effective shielding length is set by interference "edge noise' as the shield trailing edge approaches the spreading jet. In general, shielding attentuation increases steadily with frequency, following low frequency enhancement by edge noise. Although broadband attenuation is typically only several decibels, the reduction of the subjectively weighted perceived noise levels is higher. Calculated ground contours of peak PN dB (perceived noise level) show a substantial contraction due to shielding: this reaches 66% for one of the sugar scoop shields for the 90 PN dB contour. The experiments are complemented by analytical predictions. They are divided into an engineering scheme for jet noise shielding and more rigorous analysis for point source shielding.
- Publication:
-
Unknown
- Pub Date:
- May 1983
- Bibcode:
- 1983eass.book.....W
- Keywords:
-
- Acoustic Measurement;
- Jet Aircraft Noise;
- Noise Reduction;
- Point Sources;
- Prediction Analysis Techniques;
- Shielding;
- Algorithms;
- Anechoic Chambers;
- Baffles;
- Edges;
- Helmholtz Resonators;
- Integral Equations;
- Scaling Laws;
- Wing Nacelle Configurations;
- Acoustics