They'll probably have to come up for air (and food...for stamina purposes) at some point. That will give you the opportunity to leave a note on the Love Chamber door when that they'll see when they return.
"Dear -----, I hope you're having a wonderful stay here. But just so ya know: the walls are really thin here in the house. And I've been cursed with terrific hearing. 😉
Thanks in advance for your consideration.
Your sleepy host, Venus"
WIth luck, they'll crank it down a notch. We've only been hosting for two months and we've already had a couple "cheater couples" stay with us. At least they're staying in a well-insulated guest house so they could be up to all kinds of Olympic-class stuff in there and we'd never know it. But Diane sages the room afterward, just to get rid of the lingering guilt.
Good luck!