中文摘要：

有源声学结构是近年来提出的一种控制结构低频声辐射的有效方案，它是智能结构在噪声控制领域的具体应用，其控制机理是一个亟待解决的关键问题，文中结合声辐射模态和结构振动模态理论对该问题进行了研究并作了定量解释。研究结果表明：有源控制的机理在于减小结构主导辐射模态的幅度（声功率），同时保证低阶非主导辐射模态的幅度不会有大的升高；在控制高阶辐射模态幅度的同时，低阶辐射模态幅度也被有效控制；四个次级板能够抵消各种类型的振动模态对应的主导辐射模态，从而有效控制结构所有振动模态的声辐射。

英文摘要：

Active acoustic structure proposed in recent years has been viewed as an encouraging approach to actively reduce the sound radiation from vibrating structures. In this study, the mechanism of active control, which is one of the key problems in the study of such a structure, is investigated based on the theories of acoustic radiation mode and structural vibration mode. It is shown that the optimum reduction in the radiated sound power would be arrived, if the amplitude of the dominant radiation mode decrease and meanwhile other lower-rank radiation modes do not go up high. If the amplitude of the high-order radiation mode is decreased, so will also be done for the lower-order radiation modes. Four secondary panels can reduce the dominant radiation modes, that correspond to all the structural modes, and can guarantee a considerable reduction of the total sound power over the entire frequency range of interest.