Numerical Simulation Of The Indoor Sound Field And Characteristics Analysis

The boundary Element Method (BEM) is widely applied to engineering problems due to its simple computation, strong adaptability and high accuracy. In this paper, the indoor sound field is simulated numerically by BEM, and the effects of acoustic structures on the acoustic diffusion of a classroom and a vocal practice room are discussed.First, BEM models of two and three dimension regarding the interior acoustic problems are built. Quadratic discontinuous elements are employed to deal with the corners and improve the accuracy. A Delaunay refinement algorithm is improved to triangulate a simple polygon boundary effectively and uniformly. The singular part of the singular integral is separated out and is calculated analytically by the integral limit or the polar transformation. The complex system equation is solved by a combinatorial algorithm.Second, BEM programs are developed in C# language, and then validated by Morse's theory. The quadratic residue diffuser (QRD) is approximated by a transfer formula of the acoustic specific impedance, and it is validated by the whole surface modeling.Third, the acoustic field in a classroom is simulated numerically using the two dimensional BEM program. The differences of the acoustic diffusion when terraces, QRD and absorptive material of distinct parameters are employed on the ground, the ceiling and the rear wall respectively are discussed. The numerical results indicate that significant improvement of the acoustic diffusion is obtained when the three structures are combined.Finally, the acoustic field in a vocal practice room is simulated numerically utilizing the three dimensional BEM program. The effects of the ceiling shape and the absorptive material position on the acoustic diffusion are analyzed. The numerical results show that the highest average acoustic diffusion is achieved, when the absorptive material is fixed on the side wall against the lowest side of the oblique ceiling.