Here's a version for a single room. It triggers only when a player is present, and will not repeat unless they leave the room for a short time and re-enter. Note that the sound "ambient_cave1" is randomized by the server to choose between several variant dripping noises, so it will not sound the same each time.
iact name: startwaitfor player goto drip
pause 10
goto start
iact name: drippause 20
sound dproc/ambient_cave1
echo The sound of dripping water echoes through the cave.
pause 60
goto loop
iact name: loop waitfor player goto loop
pause 10
goto start