where does the sound of a fart come from
Flatulence It is normal for humans to pass flatus through the rectum, although the volume and frequency may vary greatly between individuals. It is also normal for intestinal gas passed through the rectum to have a characteristic feculent smell, although this too may vary in concentration. Flatus is brought to the rectum by specialised contractions of the muscles in the intestines and colon. The noises commonly associated with flatulence ("blowing a raspberry") are caused by the vibration of anal sphincters, and occasionally by the closed buttocks. Both the noise and smell associated with flatus leaving the anus can be sources of embarrassment or comedy in many cultures.