If the music, the sound-absorbing materials and the white noise don't work, then you may need do the simplest, and hopefully most effective, technique. Go talk to your neighbor. A lot of problems, including your noisy neighbor, can be solved with some good old-fashioned communication.
This doesn't have to be a confrontational conversation. If your neighbor plays his music too loud or too late at night, tell him that it's not the music that you don't like, but how late he's playing it. Unless you really don't like his music; then you may want to keep that to yourself. The point is that you don't have to be fuming mad and yelling to get your point across. Just state what the problem is and try to offer a solution that both of you can agree on.
If you'd rather not meet the stranger in your building that's annoying you so much, then try leaving a note for them that clearly explains the noise he's making and why you think it's an unacceptable amount.