Mechanical mobility technique

The structure-borne sound transmission of a built-up mechanical structure can be analyzed using e.g., Finite Element Methods, theoretical and experimental modal analysis methods and Statistical Energy Analysis. The method is selected depending on application and situation. The analyzis is simplified if parts of the system can be analyzed separately. This technique is called substructuring. In practice the substructuring technique should allow the use of measured input data of assembled parts. So-called impedance or mobility techniques allow substracturing and use of measured input data. This short review presents basic concepts of mobility technique. First mechanical impedance and mobility of elements is discussed. Also impedance and mobility parameters are included. Thereafter transfer matrices, which describe the force and velocity relationships of connected beam elements, is discussed. Multiport methods or transfer function methods are suited for the analysis of built-up mechanical structures coupled in junctions with small dimensions. Emphasis is given to applications in the ship context.