A Revolutionary Boundary Element Approach Based on Energy Conservation for Interior Noise Predictions

高频宽带声场的分析在建筑声学以及飞机和汽车工业中是有意义的，其中内部噪声预测和降低是重要的。 该项目将提供一种计算效率高、准确的分析工具，用于预测包含宽带高频声波的外壳中的声压级。 所提出的边界元方法的新奇在于，问题和边界条件是重铸的时间平均变量（均方压力，能量和强度），而不是随时间变化的压力和速度的数量，和无限小的来源，包括每个元素是宽带方向不相关的来源。 此外，这种方法是唯一的新兴的基于能量的边界元或有限元方法，因为它不需要假设声介质是耗散的，也不假设边界是完全漫反射的。在高频范围内分析宽带系统的困难在于它们包含大量的模式和频率。 因此，基于模态分析的方法以及传统的有限元或边界元方法在计算上变得繁琐。所提出的方法是非常有效的，因为频带中的每个频率不需要单独考虑，并且与波长相比，单个元素可以很大。 由此产生的计算效率增益是传统方法的数量级。 当阻尼水平不小时，已经为轻阻尼系统开发的替代有效方法是不准确的。 典型的结构声学系统包含显着的阻尼水平，因为大多数系统的设计，以减少振动和内部噪声水平。 所提出的方法不限于轻阻尼的情况，因此将适用于更实际的系统。智力优点：上述边界元法的发展将为高频宽带声场的分析提供一种新的工具。 这种新的边界元方法将提供一个急需的替代传统的分析，并代表了一个范式转变的方式，这些类型的声场的治疗。 此外，这种分析工具的可用性将实现更有效和准确的分析，从而促进更好的声学空间的设计，无论是房间还是车辆内部。 更广泛的影响： 拟议的工作计划包括理论，计算和实验组件。所有这些成果都将广泛传播、出版并在国家和国际会议上提出。 边界元法在建筑声学中具有商业开发和应用的潜力。 这个研究项目的另一个更广泛的影响是通过在教室和实验室中使用声学的“实践”经验将研究和教育结合起来。 学生将有机会使用根据该补助金开发的软件，以模拟他们选择的外壳中的声场，并将参与支持这项研究的实验。 本科生和研究生都将参加这项研究，特别关注代表性不足的群体。

The analysis of high frequency broadband sound fields is of interest in architectural acoustics and in the aircraft and automotive industries, where interior noise prediction and reduction are important. This project will provide a computationally efficient and accurate analysis tool for the prediction of sound pressure levels in enclosures that contain broadband, high frequency sound waves. The novelty of the proposed boundary element method is that the problem and boundary conditions are recast in terms of time-averaged variables (mean-square pressure, energy, and intensity) rather than the time-varying quantities of pressure and velocity, and the infinitesimal sources that comprise each element are broadband directional uncorrelated sources. Furthermore, this method is unique among emerging energy-based boundary element or finite element methods because it does not need to assume that the acoustic medium is dissipative, nor does it assume that the boundaries are entirely diffusely reflecting. The difficulty with analyzing broadband systems in the high frequency range is that they contain a large number of modes and frequencies. Therefore, approaches based on modal analysis, as well as traditional finite element or boundary element methods, become 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. The resulting gain in computational efficiency is orders of magnitude over a traditional approach. Alternative efficient methods that have been developed for lightly damped systems are inaccurate when damping levels are not small. Typical structural-acoustic systems contain significant levels of damping, since most systems are designed to reduce vibration and interior noise levels. The method being proposed is not restricted to lightly damped situations and therefore will be applicable to more practical systems. Intellectual merit: The development of the boundary element method that was described above will provide a new tool for the analysis of high frequency broadband sound fields. This novel boundary element method will provide a much-needed alternative to traditional analyses, and represents a paradigm shift in the way that these types of sound fields are treated. Additionally, the availability of such an analysis tool will enable more efficient and accurate analyses, and thereby facilitate design of better acoustic spaces be they rooms or vehicle interiors. Broader impacts: The proposed plan of work includes theoretical, computational, and experimental components. All of these results will be disseminated broadly, published, and presented at national and international conferences. The boundary element method has the potential for commercial development and use in architectural acoustics. Another broader impact of this research project is the integration of research and education through "hands on" experiences with acoustics both in a classroom setting and in the laboratory. Students will have the opportunity to use the software developed under this grant in order to simulate sound fields in enclosures of their choosing and will be involved in performing experiments that support this research. Both undergraduate and graduate students, with particular attention being paid to underrepresented groups, will participate in this research.