OK TMI: Why Are Some Farts *So* Loud (and Why Can I Never Predict Which Ones Will Be)?

Oops, you did it again. Despite your best intentions, you let a fart fly that was loud enough to be heard in the next room. If this embarrassing scenario happens more often than you might prefer, you’ve probably wondered why some farts are loud but others sneak out undetected.

The truth is you do have some control over it. We spoke to gastroenterologist Joseph Weiss, MD, FACP, FACG, AGAF, clinical professor of medicine at the University of California, to find out the science behind the sound (and smell) of those ear-splitting farts—and the quiet ones, too.

“The ability to control [the sphincter muscles] is also a very useful social skill to have.”—Gastroenterologist Joseph Weiss, MD

Factors that can influence the sound of your fart

Despite protestations from those who won’t admit it, you already know that everyone farts. But did you know that the sounds your fart makes may be under your control to some degree?

In general, loud farts are caused by the anal sphincter (bowel) muscles forcibly pushing air out through the anal opening. You can control the force of that action by learning how to effectively use and control these muscles. “The anal sphincter muscles control the opening size of the anus. With effective sphincter muscle control, slow and silent releases can be managed. The ability to control them is also a very useful social skill to have,” Dr. Weiss explains.

Dr. Weiss says that some people may find it more challenging to control these muscles than others, as sphincter tone can diminish with age, pregnancy, anorectal surgery, and more. “For people with reduced sphincter tone, the release of a fart can become involuntary,” he says.

Other factors that affect fart sounds include the resonance and vibration frequency generated when the fart leaves the body. “Just like a faucet or garden hose, narrowing the opening increases pressure, and the sound frequency becomes higher.”

The composition of gasses in the fart can also affect its sound. Dr. Weiss says that these are determined by what you eat, whether or not you swallow air, your gut microbiome, illnesses you have, and medications, such as antibiotics, that you take. “Volume of gas, the velocity of release, and the muffling effect of clothing and things like seat cushions also have an impact,” he adds.

How to consciously dial down the volume

To “air” may be human, but that doesn’t mean it’s okay to let it audibly rip whenever and wherever. You may not have thought much about your anal sphincter muscles before, but controlling them is the key to reducing the sound of your farts.

The anal sphincter is a ring-shaped band of muscle surrounding the anal opening. You have internal and external anal sphincter muscles. The internal sphincter is an involuntary muscle that is designed to remain shut. You can’t consciously control it any more than you can control other involuntary bodily functions, like blood flow.

The external sphincter muscle, however, is part of the pelvic floor. This muscle is under voluntary control and can be strengthened with pelvic floor exercises, like Kegels.

Strengthening your pelvic floor is beneficial for reducing involuntary urinary leakage, as well as for controlling gas expulsion. Before you start squeezing, however, see a doctor. If you’re struggling with uncontrollably loud farts or stool leakage, you may have an underlying health condition that can be mitigated with medication or dietary changes.

Okay, but why do some farts smell way worse than others?

The whole “silent but deadly” thing is pretty much a myth. Loud farts can be smelly or not, based on factors like the foods you eat, and your digestive health. All the Kegels in the world won’t alter the aroma of your toots. To do that, you may need to change your diet.

Here’s why: A fart is made up of multiple gasses. These gasses are byproducts of the foods you eat and the beverages you drink. “Major gasses such as methane are odorless. Odiferous gasses make up less than 1 percent of a fart. They include hydrogen sulfide, mercaptans, putrescence, and others,” says Dr. Weiss.

So, whose farts are typically the smelliest? People who eat a lot of meat. Dr. Weiss notes that odiferous gasses are commonly produced from the digestion and metabolism of animal fats and protein. “The farts of vegetarians are less offensive than carnivores,” he says.

Though, vegetarians aren’t totally off the hook. Beans, lentils, and vegetables like asparagus, onions, and garlic can also cause lots of foul-smelling gas. So regardless of your diet, a smelly fart is bound to sneak in every once in a while—but that’s just part of being human.