My brother had what we used to call his 'silent vacation fart'...
We would be in the family station wagon, driving along...all of a sudden, there would be this horrible smell in the car...since we heard nothing from inside the car, we assumed it something in the countryside outside the car...
Then I noticed, just before the awful smell came, my brother would roll up his car window, usually at a point when others in the car had their windows at least partly rolled up...he would then smile, and the awful smell would come...yup...he could toss those suckers out, without a sound...he said it was an art...
Now, my dad prided himself on delivering loud, but almost odorless farts...but when he smelled my brothers works of art, he would holler, "Man, that boy is just rotten inside".
Me? Oh, never, women dont fart, dontcha know?
We called 'em SBD's (Silent But Deadly)