This is the real reason we presoak beans; because yes, doing so does help reduce bean-gas - but only if you do a HOT soak and discard the resulting "bean water" before making the soup. A quick, HOT presoak helps remove some of the indigestible complex sugars in them that cause gas. If you have a difficult relationship with beans, you may find that presoaking all your beans before cooking changes that relationship noticeably for the better.  The trick is, you must do a Hot Soak, and then drain and rinse the beans, discarding the soaking water before proceeding. A COLD soak will not help with bean-gas reduction.  I have years of anecdotal evidence to back up this claim. Which is to say, I live with people (not naming any names or anything) who have more trouble than some digesting those aforementioned "indigestible complex sugars." That's probably all I need to say about that.