It's more noticeable when providers fart because butt-crack hair acts as a silencer and most of us don't have any, just ask DFWRaven
![Trampoline](https://cdn-w.eccie.net/images/smilies/modern/trampoline.gif)
He recently got the before and after test of having butt-crack hair as opposed to having it shaved smooth.
Honestly though, sometimes during sex gas will build up. Many ladies (myself included) will say they need to use the little girls room as an excuse to run in there, close the door, and hopefully get rid of the unwanted gas. We are not robots though, and sometimes during an extremely fun or action packed romp a little gas will escape. As a provider I do everything in my power to avoid slips like this, but as they say, "chit happens!"