Energy-Based Boundary Elements to Predict Broadband Sound Fields in Enclosures

高频宽带声场分析在建筑声学、预测和降低飞机、汽车内噪声等方面具有重要意义。该项目将为这些应用程序提供高效和准确的分析工具。所提出的边界元方法的新颖之处在于，它是用时间平均变量(均方压力、能量和强度)来表示的，而不是用时变的压力和速度来表示。构成每个元素的无穷小源是宽带方向不相关的能量强度源。高频宽带系统包含大量的模式和频率。因此，传统的有限元或边界元方法计算繁琐。所提出的方法是非常有效的，因为不需要单独考虑频带中的每个频率，并且与波长相比，单个元素可以很大。典型的结构-声学系统，如汽车内饰，由于其设计旨在降低振动和车内噪音水平，因此包含显著水平的减振。与许多替代方法不同，该方法不局限于轻阻尼情况，因此将适用于更实际的系统。在以前的NSF赞助下，为开发该方法的这一阶段奠定了基础，并提出了新的技术问题。该方法目前适用于镜面反射静止墙的稳态声场。这项拟议的工作将把这种方法扩展到作为声源的振动墙(例如，飞机机身)和时间衰减声场。工作计划包括理论、计算和实验部分，这将允许不同能力的学生参与进来。本科生将有机会进行声学实验。研究生将参与这项工作的理论和计算发展，这需要更多的专业知识。该研究小组将开发声学演示，用于工程学院每年几次的外展工作(面向K-12群体)。

The analysis of high frequency broadband sound fields is important in architectural acoustics and for the prediction and reduction of interior noise in aircraft and automobiles. This project will provide efficient and accurate analysis tools for these applications. The novelty of the proposed boundary element method is that it is formulated in terms of time-averaged variables (mean-square pressure, energy, and intensity) rather than the time-varying pressure and velocity. The infinitesimal sources that comprise each element are broadband directional uncorrelated energy-intensity sources. High frequency broadband systems contain a large number of modes and frequencies. Therefore, traditional finite element or boundary element methods are computationally cumbersome. The proposed method is extremely efficient because each frequency in the band does not need to be considered separately and individual elements can be large compared to a wavelength. Typical structural-acoustic systems, such as vehicle interiors, contain significant levels of damping since they are designed to reduce vibration and interior noise levels. This method is not restricted to lightly damped situations, unlike many alternate methods, and therefore will be applicable to more practical systems. Under previous NSF sponsorship, the groundwork was laid for this phase in the development of the method and new technical issues were raised. The method currently works well for steady-state sound fields with specularly reflecting stationary walls. The proposed work will extend the method to vibrating walls that act as sound sources (for example, aircraft fuselages), and time-decaying sound fields.The plan of work includes theoretical, computational, and experimental components, which will allow students of varying abilities to be involved. Undergraduates will have the opportunity for "hands on" experimentation with acoustics. Graduate students will be involved in the theoretical and computational developments of this work that require more specialized knowledge. The research group will develop acoustics demonstrations for use in outreach efforts (geared toward K-12 groups) that are given by the School of Engineering several times a year.