My parents had a lot of sex as I was growing up.
We were poor and lived in a little two bedroom house that was shoddily build. It didn't have central heat, we heated the hole house using a big wood stove in the living room. Our bedrooms were side by side, and there was a wall vent that ran between our rooms with a "decorative" cover on either side. This allow sound and light to flow between rooms, it was super annoying. We would usually keep our dirty clothes hamper in front of it to keep most of the light transfer, but it did very little for sound control.
I would often wake up to their bed slowly squeaking and mom quietly moaning as they softly made love.
Every now an again though, they would FUCK! The bed would be loudly squeaking and you could hear their bodies slapping together, making a wet thud sound. Mom was normally pretty reserved, but when they where really getting down with it she became pretty vocal. Not so much with words, but with loud, deep sounding grunts... and when she would orgasm, it sounded like she was possessed. More than once I was awoken from a dead sleep to her orgasming, it would scare the shit out of me.
I used to sneak into their room and slid their hamper over a few inches, just enough to give me a good look at their bed... These eyes have seen some things!