My housemate is a great friend, and for the most part we get along fabulously.  He got a new girlfriend a few months ago, and she's over a lot.  I like her well enough, but the issue is his room is right next to mine, we don't have the best walls, and she is *loud* during sex.  This results in me hearing very uncomfortable sounds when trying to get to sleep, sometimes when I have early morning classes the next day.  I've tried asking them to keep it down, which was met with an apology and some quiet... for a few days.  

I don't want to be a nag or not let them have their fun, so I started buying some earplugs so I could sleep better at night.  They're not too expensive (about 5 bucks and the packs have enough to last about two weeks) but college students and budgets and all... so I'm considering asking him to buy them for me.  Would I be an asshole for doing this, or is it reasonable?