Silent but Deadly 101

The oldest boy came in to the kitchen last night and proclaimed "Mom! I learned how to keep my farts silent!"
There was a part of me that really just wanted to say "Oh that's nice" and move along but still - I was curious if the boy had truly discovered the Grail of Fart Etiquette.
After all - he's a boy - they embrace their farts whereas we females tend to not be so loving toward them.
He explained the process to me but I'm not convinced it's a secret so much as the boy got lucky and didn't crank off a flapper. He alleges that he just THINKS about it and that it's all about control.
I'm going to make him some chilli and see if his method still foolproof.