I have that problem right now, I live in a student house and the walls are paper thin, I hear anything and everything that's going on.
And they, of course, can hear me. I usually watch stuff on my laptop with earphones in, otherwise they come in like "Ooo, what are you watching?" and it's irritating.
It also deprives me of a certain amount of autonomy and control over my own life, I can't usually go to sleep before 1am, because they're up and talk in the loudest voices ever, and I can't sleep in after 9am because they're up, and, well, they talk in the loudest voices ever. Bear in mind it takes me at least half an hour to get to sleep, no matter how tired I am, and I generally require at least 9 hours sleep a day... and the maths just doesn't add up.
Oh the joys of cheap living... ¬¬