Intrinsic characterization of structure-borne sound sources and isolators from in-situ measurements

The paper addresses the problem of how to characterize vibration sources and isolators with measurements made in-situ, either on a working installation or on a test bench. For example, automotive components are often characterized by test bench measurements, but there is a need to know how they will behave when coupled to components with potentially different properties in a vehicle. Ideally all components should be characterized by intrinsic properties, which can then be transferred to other installations. In the paper, some novel in-situ measurement methods for obtaining these properties are presented. First, the active properties of a source are characterized by the blocked force measured in situ. Structural dynamic properties are represented by frequency response functions (mobilities) and it is shown how, if necessary, these may be obtained by indirect measurements, for example when access to measurement points is difficult. New results for dynamic stiffness of isolators are then presented obtained using a novel in-situ measurement approach. The method allows rotational (moment) as well as translational (force) dynamic stiffness to be obtained over a wider frequency range than many test rigs. Results are validated by measurement on an ideal laboratory structure.