Water, again?

            I was sleeping very well last night until I heard the water dripping again at about 5AM this morning. That sound is really really annoying. It disturbed my beauty sleep, which I didn't have since a few weeks ago. I was still wondering where is it from because it never happened before until last few weeks. It's already the fourth time it happened. Should I call the plumber? Or it's just the drainage system? I'm not sure what it's called though. Haha