In my red notebook is this little sentence:
why are some farts louder than others? Must follow up.
So of course I went looking for the answer and found this awesome website which frankly tells you everything you need to know about farts. (I can’t tell if the website is deliberately Geocities1999 or if it just hasn’t been updated in a really really long time)
Why do farts make noise?
The sounds are produced by vibrations of the anal opening. Sounds depend on the velocity of expulsion of the gas and the tightness of the sphincter muscles of the anus. Contrary to a popular misconception, fart noise is not generated by the flapping of the butt cheeks.
Why are stinky farts generally warmer and quieter than regular farts?
Most fart gas comes from swallowed air and consists largely of nitrogen and carbon dioxide, the oxygen having been absorbed by the time it reaches the anal opening. These gases are odorless, although they often pick up other (and more odiferous) components on the way through the bowel. They emerge from the anus in fairly large bubbles at body temperature. A person can often achieve a good sound with these voluminous farts, but they are commonly (but not always!) mundane with respect to odor, and don’t feel particularly warm.
Another major source of fart gas is bacterial action. Bacterial fermentation and digestion processes produce heat as a byproduct as well as various pungent gases. The resulting bubbles of gas tend to be small, hot, and concentrated with stinky bacterial metabolic products. These emerge as the notorious, warm, SBD (Silent-But-Deadly), often in amounts too small to produce a good sound, but excelling in stench.
While you digest that, I’ll just leave you with two completely random but absolutely cracker YouTube videos of farts. Enjoy!