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.
