ABSTRACT
Analysis of the vibration and acoustic behavior of a complex structure, such as an electric motor or other machinery structures, is very useful but difficult. According to the classical vibration and acoustics analysis principles, the motion equations, and the corresponding boundary conditions for each structural element have to be established [160]. By solving these equations, the vibration displacement, sound pressure, and other relevant parameters can be obtained. As discussed in previous chapters, this approach is usually suited for the detailed analysis of the vibration and acoustic responses at low frequencies. When the structure is very complex, especially at high frequencies where a large number of vibration modes are involved in the calculations, the computing time and the resources required can be so demanding that renders the problem almost impossible to solve. For example, the prediction of the acoustic noise radiated from a full model of a small motor may take hours to solve for only one frequency step by the finite element method (FEM) and boundary-element method (BEM). Furthermore, for a complex structure, it is an arduous task to establish the motion equations and boundary conditions correctly for each structural element. This is because currently not all the practical structural elements have their equations of motion fully established and their boundary conditions mathematically described. Therefore, in pursuing the vibration and acoustic analysis for a complex structure with high frequency solutions, a statistical approach, namely the statistical energy analysis (SEA), is usually adopted.
