If there is no “popping” sound accompanying an adjustment, did the joint move? Try this: “Pop” one of your knuckles and notice how far the joint moves. Try again, and even though the joint moves just as far, there is no sound. So, whether a joint “pops” or not does not correlate with if it moved or not. Of course, it is possible that the surrounding muscles are so tight, the joint cannot be moved enough to “pop” that joint.
Check out this video on the popping noise in Chiropractic Adjustments!