Apartment Guru: How to Handle Noisy Sex-Door Neighbors

Dear Apartment Guru,

The walls in my building are paper-thin and I always hear my neighbors-whether they are arguing or being overly amorous. Unfortunately, they seem to do both a lot (although not always at the same time-not kidding). How can I bring up this subject with them without straining what is an otherwise okay living situation?

-Feeling Un-Neighborly