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

抗噪音的一个众所周知的应用是有源耳机中的噪音消除。在这里，通过抗噪声来减少声音传播(作用于用户耳朵的噪声)。在噪声发射(即从源发出的噪声)中，最常用的是诸如绝缘垫之类的被动隔音。重量和安装空间限制了该应用在300赫兹以下的频率。这一差距可以通过积极的噪音处理来弥合。计划中的研究项目与这项任务有关。结构声辐射的减少既适用于自由声场(如电力变压器辐射的噪声)，也适用于室内空间(如飞机机舱内的噪声)。这里，自适应控制系统产生用于抗噪声扬声器的激励信号，以最小化麦克风处的声压。由于声场的空间相关性，只有使用多个麦克风才能实现全局降噪。长期以来，文献中一直讨论通过局部布置机电换能器和声学换能器来实现全局降噪。全局有源噪声控制(ANC)的解决方案需要全局声量的可观测性，如弱阻尼体中的总势声能量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，同时控制总辐射声功率的局部有源有源噪声控制系统的可行性一直没有得到很好的研究，这种方法提供了显著减少换能器数量和优化换能器位置的可能性。学徒工作组的准备工作证明了总声功率的自适应最小化是可能的。这导致了研究项目的目标，即在局部安装扬声器和传感器的频率范围内，周期性激励的板结构的总辐射声功率自适应最小化。对板结构的分析和数值方法以及实验研究是其前期工作的后续步骤，并且已经从文献中获得了知识。计划中的调查构成了这一研究项目的基础，并将该原理扩展到真正的轻质结构。因此，将产生关于通过与电声执行器非接触来降低声音发射结构的全球噪声的基本经验，并为其应用做好准备。

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.