Brand new to this forum, so forgive me if this question has been asked before...

We had our upstairs bathroom remodeled about a year ago. Almost immediately, we began hearing a loud groaning noise coming from the area around the bathroom. It doesn't necessarily follow a pattern - it's happened when the shower is running, long after the tank's been filled after a flush...even when there's no one in the bathroom. Most recently it's been doing several short 'groans' at random times. The only place I hear the noise is in the vicinity of that upstairs bathroom. Any suggestions? :confused: