It usually leads to the fart making a pulsing sound, and can be infinitely more comical than a normal fart.
It also relieves slight tension on your anus, which allows you to pass gas more casually incase you have an anal fissure.
Sizookie: "LOL, yeah, it sounded like a motorbike stalling."
David: "I think some splattered on Sally's head, and she didnt even know wtf the sound was."
Sizookie: "Gotta love that bounce fart sound."