trapped air simply gets diffused and absorbed across the membranes causing no problems whatsoever or pass to the other end.. if you have no problems belching in private, you'll have no problems in public, it is a matter of muffling the sounds, the same way you do with flatus. God did create us all with those crypts of Morgagni to separate that flatus from feces. Even if it seems intuitive there is alot of mechanics there, that your descriptions simply are at odds with at times, causing some of us to be bewildered...