That does make sense about the pop being as loud as the room it's in.
A while back I read what wildheart said about it only having to go through the floor for me, and for the neighbours it has to go through a brick wall.
So I thought, okay, let's do a pop test with a latex glove. First I'll pop it in the attic bedroom with me in the room below (only has to go through floor), and then I'll pop one in another room and I'll stand in the room next to it (only has to go through brick wall), and see how it compares.
When the noise had to go through the brick wall it wasn't as loud as how it sounded when it went through the floor. In fact it didn't really sound that loud at all.
So, now, as long as it's not late at night, I do feel comfortable with having a latex glove popping session in the attic bedroom which is great. Balloons still seem too loud though, but I think I would probably feel okay with just popping one big one at the end of a latex glove popping session.