That's not considered signals and systems, at least not where I went to school (unless you're talking about fully-active suspensions, but those are very rare and highly specialized). Rather, that would be down the "dynamics" course progression -- which is bread and butter for MechEs in those lines of work. That's also extremely useful, but it's generally a different subject matter, at least until you get into graduate-level dynamics combined with upper-undergrad-to-graduate-level numerical methods.
Vibration isolation can definitely be thought of within a systems framework, although it's perhaps overkill for passive filtering as you won't be doing much in the way of feedback.
