Why do farts make noise when they come out

Whether you’re 8 or 80, passing a well-timed loud fart can be funny.

But why are some loud and proud, and some are SBD (silent but deadly)?

The sound we all know well is part physiology and part biology, and I know how to help with both.

You see, the intestines contract and move their contents, including gas, via peristalsis.

That’s how it gets through the digestive tract.

Odorous ones are due to the type of bacteria in your gut, and non-smelly ones might just be because of swallowed air.

The trick is to keep your gut healthy.

Click below for the one “stinky” nutrient that I’ve found that keeps me farting “just riiight.”

Be smart about your fart and get control of your volume today.

Until next time, like for good poop, share for great poop.

An image of a man with smoke billowing out behind him symbolizing a fart.

Farting is a fact of life. Cows do it. Dogs do it…even insects do it! In fact, cockroaches are exceptionally windy, releasing gas through their anus at least once a day. This flatulence does make noise, but you’re unlikely to notice it unless you have extremely good hearing.1

This is probably the only instance in which you’d envy a cockroach because let’s face it…humans are pretty gassy. After all, the average person farts between 14 and 23 times per day to some estimates.2 And the release is often embarrassingly easy for others to hear, though some of us are skilled in the art of letting silent ones.

But have you ever wondered why they make noise when they come out? Or why the sound varies from one to another…or why do you need to pass gas? The answers to these questions may surprise you. Let’s start with the basics.

Why do we fart?

Farting releases gas from the intestines through the anus and is a normal and necessary process. If not released, gas builds up in the intestines. In the short term, this can cause stomach pain and bloating. If it continues, however, it can damage and destroy the intestines. Consequently, you cannot survive without this sometimes noisy and smelly habit.

Causes of gas

There are two main causes of gas: the digestive process and swallowed air.

A 3d image of a human digestive system on blue background.

Digestive process and gas

Gas is produced in the colon when “good” bacteria break down certain undigested foods.

Most of the digestive process occurs in the small intestine. However, some carbohydrates, such as prebiotic fiber, cannot be completely digested. Therefore, they must be passed to the large intestine (colon).3

The colon is filled with helpful bacteria, fungi, and other microorganisms that break down these foods. This process is called bacterial fermentation, and it creates gas. The muscles of your intestine contract to push the remaining substances, including these gasses, toward your rectum. Small gas bubbles are melded into a large one along this journey. It is released through flatulence. Any remaining substances leave your body through the anus as feces.

Swallowed air and gas

You likely swallow air throughout the day, usually while eating or drinking. Most of it goes to your stomach and is released by belching. The remaining air is partially absorbed by the small intestine. A small amount then travels to the colon and is released through the anus.4

A close-up image of a man smoking a cigarette with smoke swirling around his face.

Some activities that may cause you to swallow air include:5

  • Smoking
  • Chewing gum
  • Eating too quickly
  • Drinking carbonated beverages
  • Sucking on hard candy
  • Mouth breathing due to nasal congestion
  • Hyperventilation (usually the result of anxiety or stress)
  • Strenuous exercise that causes you to “gulp” air rather than breathe it

What is digestive gas composed of?

According to Johns Hopkins, digestive gas is composed of oxygen, nitrogen, carbon dioxide, hydrogen, and sometimes methane. (Only about one-third of people have methane-generating gut bacteria)6 Up to a quarter of the gas released from your butt is oxygen and nitrogen from swallowed air. The rest is carbon dioxide, hydrogen, and sometimes methane produced by gut bacteria.7

Surprisingly, most gas vapors are odorless. Odorous gas is primarily caused by several types of sulfur compounds. For example, hydrogen sulfide gives some farts that flammable rotten egg odor. Methanethiol is an organosulfur compound produced from the digestion of red meat. It gives farts that cabbage smell. Dimethyl sulfide, on the other hand, gives farts a sweet smell. (If you’ve ever passed wind after eating Brussels sprouts, you’ve smelled dimethyl sulfide.) But other chemicals also play a role. However, the exact chemical composition of farts varies depending on your health and diet.8

An image of high-fiber foods, like nuts, broccoli, and whole-grain bread, surrounding a wood sign that reads, "Fiber."

Foods that cause gas

Undigested carbohydrates are the most common cause of gas. This is because they are fermented by bacteria in the colon, which releases intestinal gas.

So, foods that cause gas include:

  • Fruits
  • Vegetables
  • Oatmeal
  • Beans
  • Legumes
  • Nuts
  • Wheat bran
  • Cabbage
  • Broccoli
  • Corn
  • Wheat
  • Potatoes

These foods can cause a lot of gas that can be stinky and loud, especially if eaten in excess.

Why do farts make noise?

Contrary to popular belief, the sound farts make is not created by the flapping of your butt cheeks. Rather, they’re produced by vibrations of the anus as the gas passes through.

The sound is determined by two main factors: expulsion velocity and the size and shape of the anal sphincter as the gas passes through.

Expulsion velocity

Expulsion velocity, as regards digestive gas, refers to the speed at which the air leaves your body. If it’s expelled fast with force, it’s likely to be loud. That just makes sense, right?

This type of release usually just influences the volume of the sound, however. The quality and type of sound you hear are determined by the size and shape of the anal sphincter at the time of expulsion.

Size and shape of anal sphincter

Let’s start with the shape. The muscle surrounding the opening of the anus (anal sphincter) is like a musical instrument for farts. If you’re musically inclined, you probably know that the smaller the size of the exit, the higher the sound. Conversely, the larger the size of the exit, the deeper the sound.

An image of a girl's hand playing a saxophone.

Or, if this analogy doesn’t resonate with you, imagine your lips as your anus. Open your mouth and pretend you’re blowing out a candle. Notice the sound it makes. Now close your lips and blow…force the air through your lips. Notice the sound is high-pitched and maybe a little squeaky? Does this perhaps sound like some of your farts?

It’s the same concept when you “blow” a fart.

What about the size of the anus?

There are a lot of factors that influence the general size of the anus at the time you pass gas. After all, the size will be different when you’re walking around than when you’re reclining in bed.

An image of an annoyed woman holding pillows to her ears to block out the noise.

How to lower the volume of your farts

But the good news is that you have some control over the sound of your farts. All you need to do is tighten and relax your sphincter muscle as you’re releasing gas. (You probably should experiment when alone.)9 You’ll see that you can adjust the type of sound, the volume, and even the duration. See…it really is like playing an instrument!

Other factors affecting the volume

The source of the fart also affects the volume. For example, if it’s spurred by swallowed air, it will likely be loud but not so stinky. Remember, swallowed air contains just oxygen and nitrogen. On the other hand, farts created by bacterial fermentation will likely be quieter but very stinky, aka “quiet but deadly.”10

So there you have it. Although flapping your butt cheeks together may be fun, it has nothing to do with the volume and tone of your farts!

An infographic with cartoon images illustrating ways to reduce digestive gas. The infographic text is described below.

Infographic Text

Taming the Toots

Though you can never totally cease farting, nor should you try, there ARE a few things you can do to tone it down.

Eat slowly: Eating slowly and chewing each bit thoroughly keeps you from swallowing too much gas-producing air. Plus, it makes the food easier to digest, which also minimizes gas.
Move it!!! Exercise helps break up gas bubbles in your digestive system. And you don’t have to exercise long or hard. A 10-minute leisurely walk can do the job!
Ditch the straws: When you drink through a straw, you swallow more air than usual. This can lead to gas buildup in the intestines.
Don’t smoke: When you inhale smoke, you’re also inhaling and swallowing air. This can cause a huge gas buildup.
Go OTC: Some OTC remedies may help treat gas and bloating. For example, the lactase found in Lactaid can help you digest lactose. And Beano contains an enzyme that helps break down the nondigestible carbs found in beans and other foods.

End Infographic Text

Are smelly farts a good sign?

Surprisingly, smelly farts aren’t really the norm. Otherwise, the famed “silent but deadly” release wouldn’t be a thing. If you do release silent but deadly ones, it’s usually a good sign that your beneficial gut bacteria are doing what they’re supposed to do — ferment fiber — and that you’re eating fibrous food.

Foods with a high-sulfur content, such as cruciferous vegetables, can give farts a rotten egg smell. And the gas can be silent and painful upon release at times.

The foods most likely to cause farts that smell so bad they can clear a room include:

  • Broccoli
  • Cauliflower
  • Brussels sprouts
  • Onions
  • Beans
  • Cheese

If these foods cause digestive distress and smelly farts, it’s usually nothing to worry about. Try to eat them in moderation and see if that relieves the problem. But if the stench continues for a few weeks, it could signal a few health issues.

An image of broccoli in a frying plan on the stove.

Health issues affecting the sound and smell of farts

Stinky flatulence can be a sign of several health issues. Here are just a few of them.

Food intolerance/sensitivity

Food intolerance refers to an inability to digest certain foods and affects an estimated 15% to 20% of people.11 The cause varies, but it is most commonly due to a sensitivity to chemicals or the lack of specific enzymes needed to digest certain foods.

Common food intolerances include:

  • Monosodium glutamate (MSG)
  • Nitrates
  • Gluten
  • Lactose
  • Fructose

Monosodium glutamate (MSG)

Monosodium glutamate is a flavor enhancer commonly added to processed foods, particularly canned vegetables and processed meats.

The symptoms of MSG sensitivity include:

  • Bloating
  • Gas
  • Diarrhea
  • Heartburn
  • Flushing
  • Headache
  • And more

It is not clear why some people experience MSG sensitivity, but if you typically experience troubling symptoms within 48 hours of eating processed foods, see your doctor.

If you have MSG sensitivity, try to avoid processed foods as much as possible. Instead, opt for fresh whole foods that contain little to no preservatives. (They’re better for your health, anyway.


Nitrates are food additives commonly used in processed meats. They can be obtained naturally through diet. For example, an estimated 80% of nitrates are obtained from vegetable consumption. There is scientific evidence that they may have a beneficial effect on health.12 However, foods with added nitrates, like those in processed meats, may increase the risk of cancer and other health issues.

An image of a woman holding out a glass of milk with one hand and holding out her other hand like a stop sign.


The body uses a variety of digestive enzymes to break down certain foods, and if you lack this enzyme, it can make digesting a specific type of food difficult or impossible. This is the case with lactose.

Lactose, a type of sugar in dairy products, needs a lactase enzyme to break it down. Those who lack this enzyme are lactose intolerant, a condition that is very common. In fact, an estimated 30 to 50 million American are lactose intolerant.13

Symptoms of lactose intolerance include:14

  • Gas
  • Bloating
  • Stomach pain/cramps
  • Diarrhea
  • Nausea


Those with this intolerance usually lack the protein needed to absorb fructose, a natural sugar found in fruit, honey, high-fructose corn syrup, and some vegetables. Consequently, fructose ferments in the intestine, causing digestive issues.

An estimated 1 in 3 people are unable to properly absorb excess fructose.15

Symptoms of fructose intolerance include:

  • Gas
  • Bloating
  • Cramps
  • Diarrhea

By the way…if you have this type of food intolerance, you will likely experience these symptoms only if your intake of fructose is in excess of glucose. This is because glucose helps fructose absorption in the small intestine.

An image of gluten-free pastas, breads, and snacks around a wooden sign that reads, "gluten free."


Gluten is a mixture of two proteins found in cereal grains, especially wheat. Those with gluten sensitivity have problems digesting gluten. However, this differs from celiac disease, which is an immune response to gluten.

An estimated 0.5% to 13% of people may have nonceliac gluten sensitivity.16 The factors that may play a role in the development of this condition are not yet known, but it can involve digestive and nondigestive symptoms, including:17

  • Stomach pain
  • Bloating
  • Flatulence
  • Headaches
  • Brain fog
  • Fatigue
  • Joint pain
  • Anxiety

An image of a book about digestive disorders and a stethoscope.

Digestive disorders

Here are a few of the digestive disorders that can cause bloating, gas, stomach cramps, etc.

  • Irritable bowel syndrome (IBS) is a chronic disorder affecting the large intestine.
  • Celiac disease is a serious autoimmune disease that causes the body to attack the intestines if the person consumes gluten.
  • Crohn’s disease is a type of inflammatory bowel disease (IBD) that causes chronic inflammation in the digestive tract.
  • Ulcerative colitis is another type of IBD that causes inflammation in the rectum as well as the large intestine.

When to See a Doctor

Digestive disorders can signal a health emergency. Thus, if you experience gas and/or other digestive symptoms consistently for more than a few weeks, speak to a medical doctor. If, however, you notice a black stool, go to the ER of the nearest hospital, as this can be a sign of intestinal bleeding or colon cancer.

How To avoid the embarrassment of loud farts

Though you can’t totally prevent farts — loud or otherwise — there are a few ways to minimize toot embarrassment.

Reduce gas

The best way to avoid embarrassment is to reduce gas whenever possible. Here are a few ways to do that.

  • Limit your intake of gas-producing foods, such as beans
  • Eat and drink slowly
  • Avoid carbonated drinks
  • Take a walk after meals
  • Take over-the-counter medicine, such as Beano, Lactase, and Gas-X

Do #2

Flatulence is often a sign that you need to do #2. So DO it! And if you don’t have to poop, at least you’ll have the privacy to be as loud as you want.

Muffle it with other noise

If you feel a loud fart coming, make lots of other noise to mask the sound. Slam pots and pans around. Cough loudly. Sing at the top of your lungs. Turn up the music or TV.

Go to another room

If you have enough warning before a gaseous eruption, go to a room by yourself and let it rip.

Walk away

If a fart squeaks out, walk away quickly. For example, if you’re in the supermarket, look around to make sure no one is nearby. Then let your fart out and hightail it to the next aisle. It’s better for someone to walk into your gassy cloud than for you to be caught in it!

Tighten your butt cheeks

If you’re in a place where you absolutely cannot fart freely and cannot excuse yourself, such as a board meeting sitting beside your boss, you’ll need to try to hold it in.

For this method, simply sit up straight and tighten your butt muscles. If you do this long enough, you should feel the urge to fart abate. You can also use this method to release a little bit of gas at a time. However, there’s no guarantee it won’t make noise or stink to high heaven!

You should not routinely try to hold in gas, however, as doing so can cause stomach pain, bloating, excess gas, and other distressing symptoms. Trapped gas may even be dangerous to your health because it can increase blood pressure and heart rate.

Take Viscera-3

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1- Lou C. How Often Does A Cockroach Fart? Cockroach Zone. Accessed Apr 1, 2021. https://www.cockroachzone.com/how-often-does-a-cockroach-fart/

2- Hasler WL. Gas and Bloating. Gastroenterol Hepatol (N Y). 2006;2(9):654-662

3- UPMC Health Beat. What Do Intestines Do for the Body? Sep 6, 2015. Accessed Apr 2, 2021. https://share.upmc.com/2015/09/what-do-intestines-do-for-the-body/

4- Johns Hopkins Medicine. Gas in the Digestive Tract. Accessed Apr 2, 2021. https://www.hopkinsmedicine.org/health/conditions-and-diseases/gas-in-the-digestive-tract#:~:text=Belching%20is%20the%20way%20most%20swallowed%20air%20leaves,bacteria%20naturally%20present%20in%20the%20large%20intestine%20%28colon%29

5- Chittenden B. Aerophagia: Causes, Symptoms & Treatment of Excessive Swallowing of Air. Doctors Health Press. Aug 22, 2017. Accessed Apr 2, 2021. https://www.doctorshealthpress.com/general-health-articles/aerophagia-causes-symptoms-treatment/

6- Johns Hopkins Medicine. Gas in the Digestive Tract. Accessed Apr 2, 2021. https://www.hopkinsmedicine.org/health/conditions-and-diseases/gas-in-the-digestive-tract#:~:text=Belching%20is%20the%20way%20most%20swallowed%20air%20leaves,bacteria%20naturally%20present%20in%20the%20large%20intestine%20%28colon%29

7- Helmenstine AM. What Is a Fart Made Of? ThoughtCo. Jul 20, 2019. Accessed Apr 2, 2021. https://www.thoughtco.com/chemical-composition-of-farts-608409#:~:text=%20A%20typical%20breakdown%20of%20the%20chemical%20composition,Oxygen%3A%200-10%25%205%20Methane%3A%200-10%25%20%28flammable%29%20More%20

8- Helmenstine AM. What Is a Fart Made Of? ThoughtCo. Jul 20, 2019. Accessed Apr 2, 2021. https://www.thoughtco.com/chemical-composition-of-farts-608409#:~:text=%20A%20typical%20breakdown%20of%20the%20chemical%20composition,Oxygen%3A%200-10%25%205%20Methane%3A%200-10%25%20%28flammable%29%20More%20

9- Shiffer E. Why Are Some Farts Silent and Others Squeaky? Men’s Health. Jan 2, 2018. Accessed Apr 2, 2021. https://www.menshealth.com/health/a19545944/fart-noises/

10- Shiffer E. Why Are Some Farts Silent and Others Squeaky? Men’s Health. Jan 2, 2018. Accessed Apr 2, 2021. https://www.menshealth.com/health/a19545944/fart-noises/

11- Lomer, M.C.E. (2015), Review article: the aetiology, diagnosis, mechanisms and clinical evidence for food intolerance. Aliment Pharmacol Ther, 41: 262-275. https://doi.org/10.1111/apt.13041

12- Hord NG, Tang Y, Bryan NS, Food sources of nitrates and nitrites: the physiologic context for potential health benefits, The American Journal of Clinical Nutrition, Volume 90, Issue 1, July 2009, Pages 1–10, https://doi.org/10.3945/ajcn.2008.27131

13- Kloberdanz K. Lactose Intolerance FAQ. HealthDay. Dec 31, 2019. Accessed Apr 5, 2021. https://consumer.healthday.com/encyclopedia/food-and-nutrition-21/food-and-nutrition-news-316/lactose-intolerance-faq-647337.html#:~:text=For%2030%20to%2050%20million%20Americans%2C%20a%20big,to%20digest%20lactose%20as%20we%20grow%20into%20adulthood.

14-Mayo Clinic Staff. Lactose Intolerance. Mayo Clinic. Apr 7, 2020. Accessed Apr 5, 2021. https://www.mayoclinic.org/diseases-conditions/lactose-intolerance/symptoms-causes/syc-20374232

15- How to enjoy fruit with fructose intolerance. FOD Map Friendly. Apr 16, 2020. Accessed Apr 5, 2021. https://fodmapfriendly.com/blogpost/how-to-enjoy-fruit-with-fructose-intolerance/

16- Fasano A, Sapone A, Zevallos V, Schuppan D. Nonceliac gluten sensitivity. Gastroenterology. 2015 May;148(6):1195-204. doi: 10.1053/j.gastro.2014.12.049. Epub 2015 Jan 9. PMID: 25583468.

17- Brazier Y. What is a food intolerance? MedicalNewsToday. Dec 10, 2020. Accessed Apr 5, 2021. https://www.medicalnewstoday.com/articles/263965#intolerance-vs-allergy

What Are 7 types of poop?

  • Type 1: Separate hard lumps, like nuts (difficult to pass and can be black)
  • Type 2: Sausage-shaped, but lumpy
  • Type 3: Like a sausage but with cracks on its surface (can be black)
  • Type 4: Like a sausage or snake, smooth and soft (average stool)
  • Type 5: Soft blobs with clear cut edges
  • Type 6: Fluffy pieces with ragged edges, a mushy stool (diarrhea)
  • Type 7: Watery, no solid pieces, entirely liquid (diarrhea)

Types of poop one encounters is categorized by the Bristol Stool Chart. This chart is a generalized indicator of how or why different types of poops look and feel a certain way. The 7 types of poop are broken up into categories based on a 2,000-person study!

Bristol Stool Scale

Does your poo look this good? If you have Bristol Type 3 or 4 – your poop is considered “normal”!  Bristol Type 1 or 2, is where the poop is hard and difficult to pass, are indicative of constipation. Often, these types of stool can be painful to pass – but don’t worry – Doctor Poo has a recommended healthy-gut switch solution…just keep reading!

 Should you ever worry about your poop?

Always consult your healthcare provider if you have any concerns about what your poop means. People are asked to call their health care providers if: They experience severe levels of abdominal pain or discomfort with diarrhea that does not go away when you poop or fart. Also, if diarrhea is accompanied by fever of 101 degrees Fahrenheit or higher, chills, vomiting, or fainting, call your physician immediately.

What is an unhealthy poop?

An unhealthy poop is when one poops too often (hence, your doctor asking you if you poop more than three times daily) or not pooping often enough (As such, less than three times a week) and also excessive straining when pooping. Poop that is colored red, black, green, yellow, or white. greasy, or fatty stools is unhealthy.

Help fix so many of your digestive and bathroom issues, such as gas and bloating and improve your overall health with this patented molecule that is backed by Harvard Doctor’s by clicking here!

Doctor Poo Provides More Valuable Answers for Those Hard to Ask Questions Below:

An image of an adult woman coughing into a tissue at home.
A 3D illustration showing the spasms and distortion of large intestine common in IBS.

Irritable Bowel Syndrome: IBS Mucus, Symptoms, Causes, and Treatment

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An image of the poor doctor on a sign that reads, "smelly farts."