I lived in an apartment for about twelve years, and spent about five managing another complex. Noise is ... an issue.
I found that most of the time, if neighbors were bothering me with something like loud music or TV, and I politely asked them to turn it down, they did so an apologized. Sometimes you may not realize how loud your stuff is. What just made me want to spit nails was when people who were asked to turn music down responded that "It's not a noise violation, it's the middle of the day and I can do what I want." Uh.
For myself in those situations I do understand there's a time for noise. Children can't be expected to be silent all the time - they need to go out and play. But to me there's a big difference between that and, say, the constant stereo booming three doors away or the dog that won't shut up. If I could hear someone's TV through the wall, I didn't so much mind. The walls were thin. And it had to be very quiet in my apartment to hear it.
Happily during those twelve years I had a reasonably tolerable roomie in my (at the time) husband. He was actually less tolerant of noise than I, and it was more annoying to me to listen to him complain than the actual noise itself. Go figure. It's always been my opinion that an apartment complex should have clear rules about noise and times outlined for things like parties and childrens' playtime on equipment if they provide it. Then there's no question - if the noise violates the rules you contact the manager on call.
That said, I've had a few times when noise was ... different. A few years after I moved into my first place I woke up one night at around 2 a.m. to a hell of a ruckus upstairs. It was the cops busting my upstairs neighbor for dealing pot.
Another night there was an INS raid on the apartment at the other end of our block, and when I poked my head outside to see what was up I saw a bunch of guys with guns so I stayed my little ass indoors. It was kind of a rough place until another management company bought it out.