Experimental Study on Open Rotor Noise Shielding by Hybrid-Wing-Body Aircraft.

This paper presents an experimental study on open rotor noise shielding by hybrid-wing-body aircraft, with the objective of understanding the noise shielding features and establishing methods of applying the shielding data for system noise studies of hybrid-wing-body aircraft. By studying the directivity patterns of individual tones, it is shown that, although the tonal energy distribution and the spectral content of the wind-tunnel test model (and thus its total noise) may differ from those of more advanced rotor designs, the individual tones follow directivity patterns that characterize far-field radiations of modern open rotors, establishing the validity of the use of this shielding database, provided that the shielding effects are applied on individual tones. To this end, open rotor tonal noise shielding is categorized into front rotor tones, aft rotor tones, and interaction tones: not only because of their different directivities but also due to the differences in their source locations and coherence features, which make their respective shielding characteristics distinctly different from each other. To reveal the parametric trends of the hybrid-wing-body shielding effects, results are presented with variations in frequency, far-field emission angle, rotor operational condition, engine installation, and local airframe features. [ABSTRACT FROM AUTHOR]