April, it's not what you say but how you say it.
Best to address the issue when you are not feeling too emotional and suffering the affects of lack of sleep.
I didn't know my then neighbour either, he'd just returned from the Gulf war so I did leave it a few days before I addressed the issue but we could no longer put up with all the noise at night and in the early hours of the morning. I also thought that he may not even know how thin the walls were. I was very polite and fortunately he was a nice guy so we didn't have any problems after that.