Leak inside wall

Not sure what to do here and newbie to the forum. I have a shower stall upstairs and no noticeable leaks that I can see. On the floor below that stall is another bathroom. When the upper shower is running, you can hear what sounds like water dripping onto the ceiling of the lower bathroom near the corner of wall and ceiling.

Once the shower has stopped, you can still hear the continued dripping until of course it finally stops. So how do I diagnose where the leak is coming from and what do you think could be the problem?

The upper stall is tile walls and floor with the drain in the middle. No tub, just a stall. Maybe a fresh bead of caulk around the floor edge and drain?

Thanks in advance.

Well I have investigated further and found that I can also hear the dripping sound if the upstairs sink faucet is running. I ran a moisture meter on the wall and ceiling (downstairs) and had a .01-.02% moisture. After running the water, you could feel a slight moisture feeling on the wall near the ceiling. Almost like it's seeping through, although nothing visual to confirm this. I ran the meter again on the same spot and got readings of 15-20% moisture. But only in that spot and only after having the water run upstairs. I am stumped and need some help.

Does the shower drain and sink drain meet somewhere inside the wall? That's the only thing I can think of and that there's a leak in a pipe after where the 2 meet.

Any thoughts or suggestions? I would like to get this fixed without ripping the whole house apart and before more damage can occur.

Thanks.

Thought it may help to include a rough diagram. Hopefully this will help illustrate what I am trying to talk about. When the either the upstairs sink or shower is running, the circled problem area is where you can hear water dripping downstairs. Again, nothing visual to see. The drywall at the problem area , both wall and ceiling, does feel slightly softer than the surrounding areas of drywall.

Thanks for any and all help.

Drywall or plaster/lath that is getting dripped on would normally show fairly unmistakable staining and swelling.

What is below the bottom room? Can you go into the basement or crawlspace below to see whether there is water coming through somewhere?

Sometimes what you can hear is water running, gurling and dripping INSIDE the drains, or movement of pipes as they heat up or cool down.

Under the bottom room is the crawl space. I can check under there this evening. When the water is running, you can definitely hear it running inside the pipes. I sure hope that what you describe is indeed what I am hearing.

I will check the crawl space and report back. Thank you so much for answering.