TLDR: Having loud sex your kids can hear on purpose or doing it not caring if the kids can hear it, is inherently wrong IMHO.

My family was kinda open to nudity in the inner circle or at least we didn’t saw it as something “shameful” or “bad”. We were from the coast and we used to spend a lot of time at the beach, so we were used to be around each other in bathing suits or underwear. My parents were also that kind of couple where my dad used to constantly slap my mom’s ass even in front of us (as kids or even as adults). He used to kiss my mom deeply and passionately in front of us and from time to time even grab a boob playfully and doing sounds (yeah, my dad was that kind of weird dude you meet at a bar and is telling to everybody the grossest and unfunny-est jokes you’ve ever heard). So, my sister and I grew up seeing slightly “dirty” behaviours as something natural (maybe as something “lame” adults do) or, at least, something you don’t mind that much.

That being said, my parents always were careful to not have loud sex around us and we only noticed they had sex when we were like 12 and 14. Mi bedroom and also my sister’s bedroom where not contiguous to my parent’s bedroom and we had a brick house, so we were somewhat shielded against noises from my parent’s bedroom. One time, my sister’s bedroom was being remodelled so she had to move to a spare room next to my parents’ bedroom. She heard them having sex and she totally knew what they were doing. She told me the next morning and we weren’t shocked nor traumatized, just found it “funny and gross” and we laughed at the idea while she was telling me.

Now, for the traumatizing part, I had a friend at middle school wich I once had a sleep-over with. Just the two of us playing videogames at his house. Everything was normal up until like 10:00 PM when his parents went to “sleep” and as soon as we heard the door of her parents’ bedroom closing, my friend’s demeanor changed and he went somber. Then, after like 12-15 minutes we started hearing his mom moaning and the bed creaking and moving. We both stayed silent for a momment and then he put something on the tv and amped up the volume, but he looked pissed, grossed and ashamed. I tried to change subjects but obviously he wasn’t having a good time. I can’t tell if that affected him as an adult as I haven’t seen him since we graduated middle school, but at least at that momment I can tell he was having trouble with it.

So, I guess it depends in the way you do it. If it’s by mistake I can’t blame them. If it’s on purpose or without care, I think I see it as something wrong. And I think it affects the kids, not only on the long rub but in the immediate momment.