Usually - you don't know.
It's probably something else in that area, but you have to find it. I had a cam module work loose on an HTR a couple weeks ago, it sounded like the sight had a vibration. I hand-thumped the riser multiple times before I finally found it.
On that vintage of bow, I'd check the string stop mounting screws - they go through the limbs, and can back out.
I'd check the counter-weight in the cam, it may be coming loose - I'm pretty sure you don't have modules on the cam for that model of Mathews, you have to swap the whole cam out for draw length changes.
Check the axles, I believe you have keepers on each one, one may be loose, or missing - the axle can back out if the keeper is missing.
Witness mark the axle(s) to the limb, if the bearing is bad, the axle will turn in the limb - had this happen before, and it's hard to detect without a mark.
If the cam has a draw-stop, check that as well, they buzz when first coming loose.
Last edited by AH64guy; 09/04/18.