Hearing a leak but no signs of any water.

First time homeowner here, I live in a split level single family home, in southern NJ, typical for context. I can hear a trickle of water that tapers off, coming from my upstairs bathroom when we run the sink or tub (shower combo) hot or cold water. Silent when neither is run. You ca hear it clear as day from my half bath below, water kicks on and you hear a slow trickle that trails off as the water kicks off. I’ve troubleshoot a bit, open the access panel on the back of the shower and i was able to get a good look around as well check the pipes and drain for leaks, bone dry. Did the same with the sink. Went down the rabbit hole of hot vs cold vs tub vs sink vs letting it run through vs vs plugging and releasing possibilities through process of elimination, all were having some variation of the same dripping and tapering off. My next step would have to be cutting the ceiling open, which I really would Ike to avoid, what else could I be missing.