Okay, here is my stab at it just for entertainment.
In the first few weeks, I had definite "clunking", that I believe was caused by the fact that the muscles and ligaments were not tight enough to hold the two metal surfaces together all the time, and they would clunk when they came back in contact.
I could swear that I could actually hear it. This went away for me after a few weeks.
The second, and much more subtle sensation, is one that I still get occasionally. It usually happens when I first get up, and the joint is not well lubricated, but it can surprise me at other times.
It feels like the high point of the ball was not quite centered against the high point in the cup when I first weighted the leg, and as I turn or twist slightly, it slips half a millimeter, into a more centered contact. I am guilty of calling this "clunking", even though it is quite different, and is really totally silent. I guess that slipping would be a better term.
I found the early clunking to be very unnerving, and the current slipping to be more of a mildly annoying reminder.