Transmisson Path Characterization for Passive Vibration Control

Paper in proceeding, 2007

Analysis, prediction and reduction of vibration transmission in built-up structures are addressed. The sensibility to vibrations varies spatially within a structure, due to issues as passenger comfort and/or the localization of certain sensitive components or instruments. Traditionally, vibration transmission has been analyzed adopting transfer path analysis (TPA). The contribution to the vibration amplitude or sound pressure level in some particular locations from each transfer path is quantified using the transfer path operational forces and the frequency response function (FRF) of the receiving structure. TPA considering energy based quantities such as supplied power has gained popularity as it provides more stable path contributions and ranking of dominant paths. The supplied power is associated with the far-field contribution to the response, which may be used as an approximation of the complete response in the mid and high frequency range. For low frequencies however, the near-field contribution, which is associated with the reactive power, will be significant. Hence, in that case the applied power is not well suited to characterize vibration transmission. Furthermore, it is not obvious how to modify a dominant transfer path so that the vibration response or the supplied power attenuates. Generally, the system must be considered as a whole in order to avoid sub-optimization. Examples that stress the statements above are given and an alternative tool for transfer path ranking, suitable for structural optimization is proposed. A scalar vibration exposure function is defined and the transfer paths are ranked based on its gradient with respect to physical parameters associated with each path.