Quoted from vireland:
There are hundreds of fart effects already available in pro sound FX libraries. Once you work with the FX libraries, you start to recognize specific FX the sound mixers for movies and TV shows are too lazy to pitch or change so they're not stock. Here's some from Hollywood Edge (I added to an internet gif for demonstration purposes)...
It's surprising how little Science knows about farts:
Damn, Hollywood Edge. Bringing back some memories!