If you have something to talk about with whoever, and you don't want people within earshot to hear, please leave earshot of said person/persons. Otherwise it seems like you are talking about them (and I'm sure that anyone who walks in the room thinks the same way). And I think that's rude. There are many options. Go outside. Or behind a closed door. Or just save it for later at an opportune time. Plus it's just plain annoying to hear "swswswswswsw" in the background. That is all.