Vieira Ana, Snellen Mirjam, Malgoezar Anwar M N, Merino-Martinez Roberto, Simons Dick G
Section Aircraft Noise and Climate Effects, Faculty of Aerospace Engineering, Delft University of Technology, 2629 HS Delft, The Netherlands.
J Acoust Soc Am. 2019 Aug;146(2):1085. doi: 10.1121/1.5121398.
Engine noise shielding is an important measure towards low-noise aircraft configurations. Such designs are supported by prediction tools that indicate high values for shielding of engine noise. Most prediction models approximate the complex nature of engine noise to simple noise sources such as monopoles or dipoles. This work compares predictions of noise shielding with experiments using different noise sources and shielding body geometries. The experiments considered in this work concern a monopole source shielded by a flat plate and a NACA 64-008 A wing, and a propeller shielded by the same wing. Comparisons between models and measurements are made by analysis of noise levels at individual microphones and using conventional beamforming. Results show that for the monopole cases the model predictions are in agreement with the experimental data, with an average deviation of 2-3 dB. The curvature of the leading edge of the wing influences the noise shielding results. The measured values of noise shielding of propeller noise are lower than those measured for the omni-directional source. Different types of source directivity are used to approximate the propeller in the predictions: monopole, dipole and a multi-source. The dipole approximation shows the best agreement with the experiments for the case of the propeller.
发动机噪声屏蔽是实现低噪声飞机构型的一项重要措施。此类设计得到了预测工具的支持，这些工具表明发动机噪声屏蔽效果显著。大多数预测模型将发动机噪声的复杂特性近似为单极子或偶极子等简单噪声源。本文将不同噪声源和屏蔽体几何形状下的噪声屏蔽预测结果与实验结果进行了比较。本文所考虑的实验涉及由平板和NACA 64 - 008A机翼屏蔽的单极子源，以及由同一机翼屏蔽的螺旋桨。通过分析各个麦克风处的噪声水平并使用传统波束形成技术，对模型和测量结果进行了比较。结果表明，对于单极子情况，模型预测与实验数据相符，平均偏差为2 - 3dB。机翼前缘的曲率会影响噪声屏蔽结果。螺旋桨噪声的屏蔽测量值低于全向源的测量值。在预测中使用了不同类型的源指向性来近似螺旋桨：单极子、偶极子和多源。对于螺旋桨情况，偶极子近似与实验结果的一致性最佳。
