Active sound irradiation reduction into cavities

声音进入空腔，如车辆或飞机，通常是通过飞机结构，如飞机的外壳。对于平面结构的声辐射的描述，技术文献中有大量的知识可用，这些文献描述了进入声学远场的能量传输。因此，室内振动结构声辐射主动减振的方法在很大程度上是基于这些发现的。存在大量的分析、数值和实验研究。然而，事实上，结构振动与内部声学介质相互作用。就会发生能量交换。为了降低整个室内的声压，必须考虑室内动力学。这可以例如通过以解耦的声学特征向量和结构振型的形式的模式耦合理论来实现。申请人以前的工作表明，可以通过与频率无关的声辐射模式来估计声势能。以抑制声学势能为目标的控制器，对于所有频率的每个声辐射模式，必须只考虑一个振型，而不再是每个离散频率步长一个模式。这一事实使具有结构传感技术的全局性声学控制领域进入了可行性。然而，空腔尺寸、结构质量和刚度以及结构各向异性等参数对声辐射模式的影响程度尚不清楚。此外，不规则空腔几何形状(如底部圆柱体)对声辐射模式的频率依赖关系的影响也未得到解释。通过分析和数值方法系统地阐明这些关系以及实验验证是计划工作的目标。

The transmission of sound into cavities such as vehicles or aircraft is usually through plane structures, e.g. the outer skin of an airplane. For the description of the sound radiation of planar structures, extensive knowledge is available in the technical literature, which describes an energy transport into the acoustic far field. Therefore, a large part of the approaches for the active reduction of sound radiation of vibrating structures in interiors is based on these findings. Numerous analytical, numerical and experimental investigations exist. In fact, however, the structural vibration interacts with the internal acoustic medium. An energy exchange takes place. In order to reduce the sound pressures in the entire interior, the interior dynamics must be considered. This can be realized, for example, by modal coupling theory in the form of decoupled acoustic eigenvectors and structural modes. The previous work of the applicants shows that it is possible to estimate the acoustic potential energy by means of frequency independent sound radiation modes. A controller, which aims at the suppression of the acoustic potential energy, has to consider only one mode shape per sound radiation mode for all frequencies and no longer one mode per discrete frequency step. This fact puts a global acoustic control with structural sensor technology into the field of the feasible. However, it is unclear to what extent parameters such as cavity dimension, structural mass and stiffness, and structural anisotropy influence the sound radiation modes. Also unexplained is the influence of irregular cavity geometries (e.g. cylinder with bottom) on the frequency dependence of the sound radiation modes.The systematic elucidation of these relationships by analytical and numerical methods as well as experimental validation are goals of the planned work.