A fart upon exiting the rectum causes an audible whistle. This often occurs when one is attempting to be discreet and attempts to lean to the side to allow a fart to slip out silently instead a whistling noise occurs. It is often necassary to do a check wipe after a pooper whistle.
I was sitting in my cubicle after eating mexican for lunch I leaned to the side to let one slip out you know instead i just had a big pooper whistle.
I swear to god I had a pooper whistle today that sounded like a song bird!