I spent my teenage years sleeping in my closet so I didn't have to listen to my parents get it on. I can't say I wanted to listen to ANYONE have sex when I was 13, I sure as heck didn't want to hear my parents having sex!
My parents are still cutesy and hold hands etc after being married for 43+ years, and that's awesome.. still don't want to hear them boink at 37 any more than I did at 13.
Personally, I'd take whichever parents you're closer to and say "Uhm, you know that .. uhm.. at night.. I can hear you, right?" Staring at your shoes while you say it is completely optional.
Of course, this is the 2010s.. You could just text. ;)