I'm not sure whether it happens all the time or sometimes, but when on PvP servers i can hear peoples weapons reloading and clicking etc, and it sounds like they are in one place very close to me, or sometimes next to me, when in fact there is no one there.
I was trying to find a sniper on a hill yesterday and his weapon reloading was all over the hill, i went towards the sounds of the clicks, and there was nothing. The only way i found him was because his gunshots led me to him, but the clicks 5 seconds before where in a different place that was empty. For some reason it seems like those sounds come from places they shouldn't, i.e. delayed sound or misplaced sound. (nearby sounds, not a distance affecting sound travel issue).