Adaptive minimization of radiated sound power from lightweight structures with anti-noise

抗噪声的一个著名应用是有源耳机中的降噪。在这里，通过抗噪声来减少声发射（作用于用户耳朵的噪声）。在噪声发射（即从一个源发出的噪声）中，主要使用诸如绝缘垫之类的被动隔音材料。重量和安装空间限制了频率低于300赫兹的应用。这种差距可以通过主动噪声处理来弥补。计划中的研究项目与这项任务有关。减少结构声的辐射既适用于自由声场（如变压器辐射的噪声），也适用于室内空间（如飞机客舱内的噪声）。在这里，一个自适应控制系统为抗噪声扬声器产生驱动信号，以最小化麦克风的声压。由于声场的空间依赖性，只有使用多个麦克风才能实现全局降噪。用机电和声学换能器局部布置的全局降噪方法早已在文献中得到讨论。全局主动噪声控制（ANC）的解决方案要求全局声学量的可观测性，如弱阻尼体积中的总潜在声能或进入自由声场的总辐射声功率。在振动结构辐射阻抗未知的情况下，控制总辐射声功率的局部ANC系统的可行性，目前研究较少。这种方法提供了在ANC系统中显著减少换能器数量和位置优化努力的可能性。学徒工作组的准备工作证明了自适应最小化总声功率是可能的。这导致了研究项目的目标，即在80 Hz和300 Hz之间的频率范围内，使用局部布置的扬声器和传感器，自适应地最小化周期性驱动板结构的总辐射声功率。分析和数值方法以及对板结构的实验调查是自己初步工作的后续步骤，并且已经从文献中获得了知识。计划中的调查构成了本研究项目的基础，并将该原则扩展到真正的轻质结构。因此，将产生非接触电声致动器的声发射结构整体降噪的基本经验，并为其适用性做好准备。

One well-known application of anti-noise is the noise cancellation in an active headset. Here, sound immission (noise acting at the users ear) is reduced by anti-noise. In noise emission (thus noise emitting from a source) passive sound insulation such as insulation mats are used mostly. Weight and installation space limit the application at frequencies below 300 Hz. This gap can be closed by active noise treatments. The planned research project concerns with this task.Reduction of the radiation of structure-borne sound is both applied in free sound fields (e.g. noise radiated by electrical transformers) as well as in indoor space (e.g. noise within an aircraft cabin). Here, an adaptive control system generates actuation signals for anti-noise loudspeakers to minimize the sound pressure at microphones. Due to the spatial dependence of the sound field, a global noise reduction is possible only by the use of many microphones.The global noise reduction with a local arrangement of electromechanical and -acoustic transducers has long been discussed in the literature. Solutions for global active noise control (ANC) require the observability of global acoustic quantities such as the total potential sound energy in a weakly damped volume or the total radiated sound power into the free sound field. The feasibility of a local ANC system with unknown radiation impedance of the vibrating structure, while simultaneously controlling the total radiated sound power, has been poorly studied up to now.This approach offers the possibility of significantly reducing the quantity as well as the effort for position optimization of transducers in an ANC system. Preparatory work of the apprentices working group proves that adaptive minimization of total sound power is possible.This leads to the aim of the research project, that is the adaptive minimization of the total radiated sound power of a periodically-actuated plate structure in the frequency range between 80 Hz and 300 Hz with locally arranged loudspeakers and sensorsAnalytical and numerical methods as well as experimental investigations on a plate structure are the consequent step to the own preliminary work and already gained knowledge from the literature. The planned investigations form the basis for this research project and for the extension of the principle to a real lightweight structure. Thus fundamental experience about global noise reduction of sound emitting structures by a non-contact with electro acoustic actuators will be generated and prepared for applicability.