The property of the hybrid active silencer relies on the equivalent impedance at the secondary sound source position and the impedance distribution characteristics of the one-chamber pipe itself.

研究结果表明，复合有源消声器的消声效果取决于次级扬声器位置的等效声阻抗以及无源式消声管道本身的阻抗分布特性。

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He hears a noise at the window. Here is the beginning of the poem: Once upon a midnight dreary, while I pondered,weak and weary,Over many a quaint and curious volume of forgotten lore -- While I nodded,nearly napping, suddenly there came a tapping, As of some one gently rapping -- rapping at my chamber door.

VOA: special.2010.10.31

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