I'm not an expert but I do work on bows quite a bit, and I do have a small bow shop. If it is in fact "string noise" you have a few possibilities.
1. Did you change anything on the string? If so change it back and see if that fixes the problem.
2. If your bow is in the lower poundage range ie. less than 50 lb draw wieght (especially if your letting it down from its max draw weight) then yes this could be string stretch, but not likely, and yes tightening it up would fix it as you have probably lost a couple of pounds with the stretch.
3. If you have been shooting the same bow for 3 years you should check for cam lean. That is hold your bow straight up and down and see if your cams are tilting at a different angle than the string. If so you will need new axels to fix the problem.
4. Bent cams. Check your cams to see if they are bent. With the light wieght materials that bows are made of it only takes 1 not so healthy thump on the gound/a tree/dropped case..... to bend one.
5. Mabye this should have been first, but if you have been shooting the same string for 3 years you need to replace it.
6. If you use rubber string silencers check to see if they are broken or worn out, and replace as needed.
7. If it is not any of these then it is probably not string noise, but somthing else loose on your bow. Personally I take every screw out of any new bow I get and put blue lock tight on all the threads. It has never failed me.
Hope this was helpfull.