Over the last 15 years, over-the-rotor acoustic treatments have been evaluated by NASA with varying success. Recently, NASA has been developing the next generation of over-the-rotor acoustic treatments for fan noise reduction. The NASA Glenn Research Center's Advanced Noise Control Fan was used as a Low Technology Readiness Level test bed. A rapid prototyped in-duct array consisting of 50 microphones was employed, and used to correlate the in-duct analysis to the far-field acoustic levels and to validate an existing beam-former method. The goal of this testing was to improve the Technology Readiness Level of various over-the-rotor acoustic treatments by advancing the understanding of the physical mechanisms and projecting the far-field acoustic benefit.
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机译：在过去的15年中，NASA评估了旋翼式声学处理方法，并获得了不同程度的成功。最近，美国宇航局一直在开发用于降低风扇噪音的下一代超转子声学处理。 NASA Glenn研究中心的高级噪音控制风扇被用作低技术准备水平测试台。使用了由50个麦克风组成的快速原型导管阵列，用于将导管分析与远场声级相关联并验证现有的波束形成器方法。该测试的目的是通过增进对物理机制的理解并预测远场声效，从而提高各种旋翼声处理的技术准备水平。
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