If you keep reading this forum, you will keep finding out that poly relationships and entanglements are whatever you want them to be. More experienced peeps here can share how they live, but from reading here and talking to other poly people, I have learned that you can be involved in pretty much any poly dynamic with or without everyone all living together. There's no rule that any member of a triad, vee, or quad, etc. must cohabit.
And as far as there being sex going on within earshot, lots of people have posted here about being uncomfortable with that and so they come up with guidelines and ground rules. If you don't want to hear it, you don't have to. Seems that some people don't have sex where their SOs can hear them, or they go to a hotel or some other place - OR the one person not having sex with the others finds things to do to occupy their time and leave for a while (movies, boys' night out, etc.).
Hot chick in the city.
Oh, oh, can't you see? Love is the drug for me. ~Bryan Ferry
"Love is that condition in which another person's happiness is essential to your own." ~Robert Heinlein