Energy methods

The approaches mentioned above (mass-spring diagrams, finite element calculations) are all deterministic, in the sense that they aim to precisely characterize the vibratory state of a structure at a given instant.

In general, this information is more detailed than the engineer would like: in the end, it doesn't matter what the precise frequency of the modes is (which is usually fraught with uncertainty), he just needs to determine an overall vibration level characteristic of a given operating state.

It is therefore interesting to reason in terms of energy flow between the various components of the structure. This eliminates the need for a point-by-point description of vibrations, while focusing...