Burping

Burping, also known as belching, ructus, or eructation, involves the release of gas from the digestive tract (mainly esophagus and stomach) through the mouth. It is usually accompanied with a typical sound and at times an odor.

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Physiology

Burping is typically caused by eating or drinking too fast, and thereby swallowing (aerophagia) and subsequently expelling air, in which the expelled gas is a mixture of nitrogen and oxygen. Burps can also be caused by imbibing carbonated drinks such as beer, soft drinks, or champagne, in which case the expelled gas is carbon dioxide from the drink itself. However, symptoms such as dyspepsia, nausea, and heartburn may be relieved by belching.

The sound of burping is caused by the vibration of the cardia (esophageal sphincter) as the gas passes through it. The current Guinness world record for the loudest burp is 118.1 dB, set by Paul Hunn from London, England in 2000.^[1] (This would be noticeably louder than a chainsaw at a distance of 1 meter.)

Social context and etiquette

In most of world, audible burping is not appreciated much and therefore considered to be somewhat impolite (although generally not as much as flatulence). Some people will cover the mouth with their hand in the same fashion as one used to guise a yawn. However, burping is viewed as acceptable and humorous among young children and some young adults, who see burping as funny. Sometimes, children engage in burping activities such as contests to determine who can produce the loudest burp, the longest burp, the most guttural burp, the burping of words, songs, or even the alphabet.

Some cultures do not consider burping rude at all, and may even consider it a sign of appreciation to audibly burp after a meal.

Infant burping

Babies are particularly subject to accumulation of gas in the stomach whilst feeding, and this can cause considerable agitation to the child unless it is burped. The act of burping an infant involves placing the child in a position conducive to gas expulsion (for example holding the infant up to the adult's shoulder, with the infant's stomach resting on the adult's chest) and then lightly patting it on the lower back so that he or she burps.

Because burping can cause vomiting in infants, the burp cloth or burp pad is sometimes employed on the shoulder to protect the adult's clothing.

"Burped" speech

It is possible to voluntarily induce burping through swallowing air and then expelling it, and by manipulation of the vocal tract produce burped speech.

While this is often employed by children as a means of entertainment or competition, it can also act as an alternative means of vocalisation for people who have undergone a laryngectomy, with the burp replacing laryngeal phonation. This is known as esophageal speech.

In animals

Many other mammals, such as cattle, dogs, and sheep also burp. In the case of ruminants, the gas expelled is actually methane produced as a byproduct of the animal's digestive process. Anaerobic organisms such as Escherichia coli (E. coli) and methanogenic archaea produce this effect. An average cow is thought to emit between 542 litres (if located in a barn) and 600 litres (if in a field) of methane per day through burping and exhalation, making commercially farmed cattle a major contributor to the greenhouse effect. 95% of this gas is emitted through belching.^[2] This has led scientists at the Commonwealth Scientific and Industrial Research Organisation of Perth, Australia, to develop an anti-methanogen vaccine to minimize methane in cattle burps.^[3]

Some fish are also known to expel air from their gills; here the burp is produced by gas being expelled from the gas bladder.

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