Yeah, man that sounds really tuff!! I dont really know how i would deal with that! I dont live with my partner(s) so that isnt something that would come up really. A while ago my primary was dating someone who lived out of town, she would come into town to visit every so often and usually they would stay at my primaries place but that changed when my primary moved into a room with a friend... So we discussed them both sleeping at my house in the guest room one night and it worked out great! Although my room was on a different floor entirely so it would've been difficult for me to hear anything from them.
Anyways, i guess that is a different experience altogether, sorry! I do like what Chimera said, asking about whether you had discussions about any of this before making the descision to move in together, and it is true that some people can deal with these types of things better than others, some people just can't and that is okay. But it definitely means that living arrangements need to be re-examined!
Im sure that you have all already had conversations about how you'd all like to share space and what it means for all of you to feel good and safe in that space. But maybe it'd be a good thing to talk about again and re-negotiate? I feel like talking about how you are trying to work through hearing them have sex, but it is a struggle for you would be totally valid and an okay thing for you to say to them. I don't think it is the end of the world if they have to be a bit more conscious about how much space they are taking up by having loud sex! I feel like most people would be able to understand and empathize with how hard that would be to hear.. it doesn't mean they have to feel guilty about the sex they have but it feels like everyone's emotions need to be taken into careful consideration! Just be honest and have a conversation about it is what i would probably do.
Hope this helps somehow!