Noise Shielding Assessment of Hybrid Wing-Body Aircraft Configurations

Abstract

This paper presents amethod based on theKirchhoff diffraction theory to predict the shielding of turbomachinery noise by the airframe of an advanced aircraft configuration. The key feature of this method is the fast computational time, even at very high frequencies, which makes it a useful tool to rapidly assess the noise footprint of an aircraft design. The offline part preprocesses the three-dimensional shielding geometry into a contour of its outline based on the source line of sight. Given this contour, the online part calculates the noise attenuation at a particular observer location and source frequency and can be called multiple times by an aircraft noise prediction program to add shielding estimates to its effective perceived noise level calculations. This method is most accurate for flat shielding objects characterized by edge-diffraction rays, rather than smooth, rounded objects characterized by creeping rays; shielding differences of up to 3 dB were observed in calculations using a sphere and a disk. Finally, the method is applied to a hybrid wing-body aircraft to assess and quantify the noise shielding benefit of its large planform area.