When I got my K-5II I thought the shutter was a bit loud compared to a K-5 I had handled (+ youtube videos), but since that was a whole year before I thought nothing more of it, especially since the camera worked great.
But I've just now been trolling around with the burst mode, and in the middle of a full burst (after something like 15 shots) the actuation sort of "slipped". Like there was 1,5 of a mirror actuation in the time frame of one. I'd like somebody to take a look at this video and tell me if the shutter activation seems loud, since that would mean sending in for repairs (not doing it just because of this one error).
You can adjust the volume according to the 'fart' the camera makes when turning on.