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

高频宽带声场的分析在建筑声学以及飞机和汽车内部噪声的预测和降低中是重要的。该项目将为这些应用提供高效、准确的分析工具。 所提出的边界元法的新奇在于，它是制定在时间平均变量（均方压力，能量和强度），而不是随时间变化的压力和速度。 组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。典型的结构声学系统，例如车辆内部，包含显著水平的阻尼，因为它们被设计成降低振动和内部噪声水平。 与许多其他方法不同，该方法不限于轻阻尼情况，因此将适用于更实际的系统。 在以前的NSF赞助下，为该方法的开发阶段奠定了基础，并提出了新的技术问题。 该方法目前适用于稳态声场与镜面反射固定壁。 拟议的工作将扩展的方法，振动壁作为声源（例如，飞机机身），和时间衰减声场。工作计划包括理论，计算和实验组件，这将允许不同能力的学生参与。 本科生将有机会“动手”实验声学。 研究生将参与这项工作的理论和计算发展，需要更多的专业知识。 该研究小组将开发声学演示，用于工程学院每年多次提供的外展工作（面向K-12团体）。

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.