Until I moved to the attached house I am in now, I have always lived in apartments or flats so I am used to other people around me.
Our neighbours are very quiet, elderly people and we are the "noisy" ones. When we first moved in, one of our neighbours, whose wife is very poorly, complained about us opening and closing doors at night - we weren't slamming, just opening and closing the bathroom door, etc.
He has also complained about DH watching films at night so DH put tapestries all around the TV room to dampen the noise when we he watches TV or plays with his XBOX.
Our tenancy agreement also doesn't allow us to perform any noise-making activities - e.g. Hoovering, using the washing machine, after 9PM, which is a pain because I work all day and could use the time to get chores done. (When I lived in Brooklyn, "quiet time" was after 11PM on weekdays. Sometimes I didn't get home from work till 9.)
I also have to be careful not to do things like opening and closing cupboard doors too loudly because the neighbour will complain.
Or if we are out on the weekend and come home very late, we have to be careful about how loudly we open and close the front door and how much noise we make coming up the stairs, etc. (It sounds like DH and I are teenagers - we are in our 40s.)
When I have lived in flats/apartments in both the US and the UK I have only ever complained if people were making noise - and I mean real noise, like hammering for hours or blasting music so loud my walls shook - after midnight on a weeknight. (If I thought someone was in danger, I would call the police, but that's different.)
I also think that there is a big difference between noise on the side of you and noise that is pounding over your head.
Our neighbours on both sides never seem to make a peep. The only thing I ever hear is sometimes the light switch being turned on in the bathroom if I happen to be in my bathroom at the same time.
Maybe I am so used to hearing other people that I don't notice little noises.
In fact, when I am home alone, I find the fact that I don't hear other human voices or other people walking around to be creepy.