i'm having the same issue. here are my specs:

i7 3770 @ 3.4Ghz
16GB DDR3 1600Mhz
HD7750 1GB DDR5 Radeon GPU
250GB HDD

when i spawn in, it will run perfectly for a few minutes, it will gradually stutter almost like its accessing the HD as if the system is low on memory. worked great before the latest patch. when i log out of the game and restart and go back in, it does the same thing all over.

memory leak?

i7 3770 @ 3.4GHz
8 GB DDR3
Radeon 7750 1GB DDR5
Win 7 64bit

Massive fps drops when in bigger cities with the empty apartment complex buildings down to 17-25 fps. Smaller towns I average 30-45 fps, open fields and some woods 60+ fps.

I'm running with the settings mostly in the low range with a few things on medium. I've tried bumping things up so the gpu would try and take over more but it made it worse.

i too have noticed when i'm in my comfy little hiding place, i faintly hear someone eating (the chomping sound) over and over. occasionally i'll hear bullets being separated or a can opening almost as if someone was right next to me. freaks me out!