You could be hearing the water running threw the drain pipe and might not have a leak or if you think it is a leak then it could be leaking and following the pipe down threw the pipe holes but at sometime it will show where it is leaking.
Many times if the piping used is non ferrous you can hear the water flowing THROUGH the piping and it can sound like a drip. To find a possible leak you should fill the tub and basin and allow them to drain at the same time as this will normally get the full volume needed to find any defects in the drainage systemIf the tub has a shower as well, the pipe from the faucet to the shower head could be leaking. You might also check the tube that comes OUT and fills the tub. It could be leaking back at the valve when you turn on the water.
The drain is plugged somewhat between the upstairs and downstairs. Need to snake the drains.
You have to remove the ceiling below to rough in a new shower above.
A drain leak, a leaking shower pan, a leaking shower valve or piping, a leaking bezel or escutchions on the shower valve, bad or missing grout, bad caulking in the corners of the wall, a leaking shower door, water spilled on the floor, or, a drain pipe leak. any one or combination of the listed problems can do it. Look things over take care of what you can see wrong before making a hole in the ceiling. If you think you have fixed the leak repaint the stained area but prime 1st with Kilz or Binz to cover the stain or it will reappear through the paint even if the leak has stopped. If the leak hasn't stopped from taking care of the things you could see then open up a hole to see where it is coming from.
Shower body or pan not properly supported or the joint not properly caulked possibly a fiberglass pan with plastic piping
typically shower drains are 2"
If it is indoors and not a recessed shower, you may have a leaking shower pan.
The Bobrick shower curtain cannot be installed in the ceiling. It is made be installed in the shower wall brackets.
A leaking shower valve by installing a new cartridge.
The shower gurgles because the water is going down the pipes.
There are several possibilities; some of them indicate plumbing problems, and some of them are just consequences of physics. If the ceiling in the room with the shower drips all over during a hot shower, it may simply be that water vapor from the hot water is condensing on the relatively cool ceiling and dripping. If the ceiling in the room with the shower drips in a particular place, then it may be that the hot water pipe is leaking. (It's unusual for the hot water pipe to run through the ceiling instead of running up inside the wall, but it's not impossible.) It's also possible that it's condensation again, but that the condensation is only occurring at a particularly cool spot... perhaps where the ventilation system or a cold water pipe runs through the ceiling above. If the ceiling in the room underneath the shower drips after someone takes a shower, but only a hot shower, again it's probably the hot water pipe. If the celing in the room underneath the shower drips regardless of whether hot or cold water is used, then it's most likely a drip in the shower drain pan.
There is a clog between the sink and the line to the street or septic tank. The sink is the easier path for the upstairs shower.