Modal quantities and their usage for evaluation of radiated sound power

振动结构发出声音。辐射声功率是量化这种声音的量度。它是一个全局量，这使得评估成本很高，特别是在需要在频率范围内解决问题的情况下。这是一个结果的事实，即系统矩阵依赖于频率隐含在大多数配方的外部声学问题。因此，在这些情况下，几乎不使用类似于解决内部声学问题的模态方法。在外部声学中有两种类型的模式。这些是频率相关的辐射模式和频率无关的正常模式。这两种方法都很适合作为辐射声功率重建的基函数。然而，这些模式的异同几乎没有研究，因此，几乎不知道。很明显，如果结构参数得到控制并且流体几何形状保持不变，则两者都非常适合用于频率范围内的分析和结构声学优化中的应用。该项目将从一个工作包开始，为评估频率相关辐射模式和频率无关正常模式提供工具。第二步包括对简正模进行更详细的研究，了解它们的物理性质。预计第二步的结果允许理解两种类型模式的相似性和差异。该项目的关键部分在于寻找标准，将频率无关的正常模式分类为与辐射声功率评估相关或不相关的模式。关于与辐射声功率相关的模态的知识对于频率范围内的模态叠加和结构声学优化是有价值的。

Vibrating structures radiate sound. The radiated sound power is a measure to quantify this sound. It is a global quantity, which makes evaluation costly in particular in cases requiring solution over a frequency range. This is a consequence of the fact that system matrices depend implicitly upon frequency in most formulations for the exterior acoustic problem. Therefore, modal methods similar to solution of the interior acoustic problem are hardly used in these cases. There are two types of modes in external acoustics. These are the frequency depending radiation modes and frequency independent normal modes. Both of them are well suited as basis functions for reconstruction of the radiated sound power. However, similarities and differences of these modes are barely studied and, thus, hardly known. It is just clear that both are well suited to be used for analysis over frequency ranges and for application in structural-acoustic optimization if structural parameters are controlled and the fluid geometry remains unchanged. The project will start with a working package to provide tools for evaluation of frequency depending radiation modes and frequency independent normal modes. The second step includes a more detailed investigation of normal modes understand their nature with respect to physics. It is expected that the results of the second step allow to understand similarities and differences of both types of modes. Crucial part of the project consists in finding criteria to categorize frequency independent normal modes into modes to be relevant or not relevant for evaluation of the radiated sound power. Knowledge about the modes being relevant for the radiated sound power can be valuable for modal superposition over a frequency range and in structural-acoustic optimization.