This paper investigates the performance of active noise control (ANC) systems with two reflecting surfaces that are placed vertically on ground in parallel. It employs the modal expansion method and the boundary element method to calculate the noise reduction of the systems with infinitely large and finite size reflecting surfaces, respectively. Both experimental and simulation results show that the noise reduction of the system can be significantly increased after optimizing the surface separation distance and their locations with the sound sources. It is found that the sound radiation of the primary source can be completely reduced in principle if the surface interval is less than half the wavelength and the source line is perpendicular to the surfaces for infinitely large reflecting surfaces. Even with finite size ones, the noise reduction performance improvement is still significant compared with those without any reflecting surfaces. For example, for an ANC system with a source distance of 0.074 m, experiments achieve an improvement of 8.6 dB at 800 Hz where two 0.2 m × 0.2 m parallel reflecting surfaces are placed with a distance of 0.15 m around the system on ground. The mechanisms for the performance improvement are discussed.

中文翻译：

---

有源噪声控制系统在具有两个平行反射面的地面上的性能。

本文研究了有源噪声控制（ANC）系统的性能，该系统具有两个平行于地面垂直放置的反射面。它采用模态展开法和边界元法分别计算具有无限大和有限尺寸反射面的系统的降噪。实验和仿真结果均表明，优化表面分离距离及其与声源的位置后，可以显着提高系统的降噪效果。已经发现，如果表面间隔小于波长的一半，并且源极线垂直于无限大反射表面的表面，则原则上可以完全减小主源的声辐射。即使是有限尺寸的 与没有任何反射面的产品相比，降噪性能的改善仍然非常显着。例如，对于源距离为0.074 m的ANC系统，实验在800 Hz时实现了8.6 dB的改善，其中两个0.2 m×0.2 m平行反射面以0.15 m的距离放置在地面周围的系统中。讨论了提高性能的机制。