Most people I’m sure have had a situation where they either heard their neighbor or roommate having sex next door.
But to see them is taking it a notch up.
You should just politely let your neighbor know you can hear them.
Maybe if you’re too embarrassed to tell them face to face, you could pop an anonymous note through their door.
There is nothing illegal in having sex with your lights on or being very noisy, to say the least.
So, if they take no heed to your complaint, then you need to begin to find ways to work around it.
For your sake, I hope these episodes last no longer than twenty minutes.
And no, I don’t think they are trying to send you any message because as you claim, the neighborhood is crowdy and may people live in the area.
I, however, think they are just two grown freaky people who are too drenched in their sex life to even consider people like you, who are offended by the moans of passion and lack of privacy.