Experimental study of shielding of propeller noise by a wing and comparison with model predictions

Abstract

The shielding of engine noise by the airframe of an aircraft is considered an effective way of reducing noise levels on the ground. Noise shielding in conventional aircraft is mainly due to the presence of the wings and most model predictions of full-scale aircraft neglect the effect of the airfoil curvature. The engine is typically simpliffied as a point source. The objective of such approximations is to reduce the complexity of the model implementation and to decrease the computational time. Measurements of noise shielding of a model wing took place in an anechoic facility using a microphone array. Two noise sources are considered: a point source and a model propeller. These measurements assess differences in noise shielding between using a point source and a source with strong directivity as a propeller. The comparison of experimental data with model predictions ascertain whether the simpliffications commonly used in noise shielding problems are realistic. The noise shielding predictions use a method based on the Kirchhoff integral and the Modiffied Theory of Physical Optics (MTPO). This work aims to understand, using experimental data, possible limitations of noise shielding predictions when adopting typical simpliffications.