Don't listen to my husband.
When your baby's tummy is exposed, and you place your mouth on the soft expanse and proceed to blow air so as to create the sound of flatulence, that is known as a poost. If you do the same, on a smaller scale, perhaps to someone's cheek, with lips puckered (not wide open), such an act is termed zerbet.
Poost and zerbet can coexist, and, indeed, they are related. There is an important distinction, however, and we must never call a zerbet what is most clearly a poost.
The cardboard tube found giving shape to your paper towels or wrapping paper is known as a do-do. That is "do" pronounced "doe." For when one places one's mouth in one end of the tube and makes sounds like a trumpet, one says "do-do."
One most certainly does NOT say "doo-doo," for such a scatological reference is loathsome and most undesirable.
Do not listen to my husband.