1st Marriage: The woman thinks she needs to fart.  She goes to the bathroom, closes the door, runs the tap to disguise the sound, wads up some toilet paper, and uses the paper to muffle any additional noise.  Then she sprays air freshener in the event of any odor, and leaves ther bathroom with nobody the wiser.

2nd Marriage: She gets up, goes to the bathroom, leaves the door wide open, and says "Excuse me" in response to the sound of a tugboat making its way through your apartment.

In the 3rd marriage, I'm guessing she doesn't bother getting up at all...and might not say excuse me.