When we learn our tools well enough, we can tell when someting isn't
quite right, just by a small unusual sound emanating from it, somewhat
similarly as knowing a saw blade is getting dull, because it makes
more noise than previously.... more noise than a sharp one.
Yep, always check out the source of an unusual sound, no matter how
slight. Though I don't recall a personal incident, this practice
probably applies to unusual/unfamiliar vibrations, also.
And, if I may add, when using a (box, other) fan, to cool yourself as
you work: first, check the breeze direction so that your shirt tail
doesn't blow/flap near the jointer blades/head, as recently happened
to me (no accident, however), before engaging in the work... or blow/
flap near your saw blades, etc.