On the draining of resonance.....

I have read of the importance of controlling resonance in components that contain motors and transformers. This seems to involve placing isolation points or bearings under components to attract or "drain away" micro vibrations, I suppose, of resonating frequencies. Ok--say this works, but hasn't the resonance already occurred as it is being drained away through the bottom of the chassis? I get the idea of isolating out airborne vibrations carried by the rack, stand, plinth, block, etc, but......really?