My question is about plumbing. My facebowl makes loud noises after each use. What gives?

Answer 1

It's burping from drinking too much water... going down the drain...
You may seriously, have a partially blocked vent pipe (on the roof... snow, ice, bird nest?) or there may be a partial clog in the drain... or the pipes may be banging inside the walls because the plumber that put the pipes in didn't attach them to the wall studs with clamps.

Answer 2

Is the stack vent clogged? You may have to go up on the roof to check. It may be best to hire a bonded professional.

The inspectors required a pressure check when our house was new. Some yoyo forgot to remove the caps on the stack vents and we had noises for years before we figured out what the problem was.

I've heard that birds sometimes build nests atop these vents and clog them.