My youngest is obviously a very good lover - or all his girlfriends are particularly excitable. It usually wakes me as it's about the same frequency as a baby crying (or a cat howling).
Once I took the opportunity to go to the loo at 5 am, and flushed very pointedly, then went downstairs to get a glass of water
DS,obviously a little embarrassed, came down and asked me why I was up, wearing jeans but no top. I said I usually have trouble sleeping and often got up, and didn't mention the disturbance.
I had to giggle to myself though as he turned round to go back up - trailing a lacy bra out of the back of his jeans, like the tail of the devil!