i can hear water dripping sound every 5 seconds from unfinished basement ceiling but i don't see any water stains or moisture on ceiling. The sound come from inside the sub floor. Bathroom is located above the sub floor where the sound come from.
We moved in three weeks ago and The dripping sound been three weeks.
Please help me what is the sound. Water dripping or something else?

do you hear the sound 24 hours a day or does it come and go periodically.
do you have hot water baseboard heat?
does it happen when someone runs hot water in the bathroom.
reason for questions is that pipes expand and contract with temperature changes of the water inside them. when/if they rub against wood they move and make a ticking/clicking sound giving the appearence of a leak..

Or it could be a leaking flapper in the toilet, and the water is dripping into the stool hub. Adding some food coloring to the tank of the toilet to see if it infiltrates into the bowl will show whether you have a leak with the flapper.