Multi–domain Boundary Element Method in Acoustics

This chapter reviews the development and applications of the multi–domain boundary element method in acoustics. Early development of the method originated from the need for solving problems involving two or more acoustic media, as well as radiation and scattering from thin bodies. The concept of the multi–domain method may be simple, but real implementation could be tedious when one has to define many subdomains and match many interface boundary conditions. As new techniques for regularizing the hypersingular integral equation became more available in the early 1990’s, thin–body problems no longer required the multi–domain boundary element method. A so–called direct mixed–body boundary element method was also developed to handle a mix of regular and thin bodies. Later, problems involving two or more acoustic media could also be solved by an extension of the mixed– body concept. Nevertheless, the multi–domain boundary element still remains to be a viable choice today. When implemented in a modular way using the impedance matrix approach, the multi–domain boundary element method is very efficient and requires only a small amount of computer memory. Instead of being totally eliminated, the multi–domain boundary element method has actually become more powerful and easier to use when used in conjunction with the direct mixed–body boundary element method. Recent examples in muffler and silencer analysis are used to demonstrate the idea.