A noisy stomach is usually caused by gas. It is the gas that makes a person burp or make noises from another more embarrassing end of their body. It's also responsible for growling or rumbling stomachs, often at the most embarrassing moments. No one is gas-free, but some people seem to have louder stomachs than others.
The gas that makes so much noise is usually caused by the ingestion of air; the rest can be formed as a normal part of food digestion. While most people don't swallow air on purpose, many do swallow quite a bit while doing ordinary things. For example, many people swallow air while speaking. Those who inhale through their mouths as they speak tend to swallow more, and people who gasp excitedly as they speak may take in even more. This can lead to burping that seems excessive and a very noisy stomach.
People also tend to swallow air while eating. This is particularly true for those who eat and talk at the same time. A person is also likely to swallow air while smoking and chewing gum. Drinking through a straw and wearing ill-fitting dentures can also lead to this problem, as can drinking a lot of soda and other carbonated beverages.
In some cases, a medical condition contributes to air swallowing and the development of a noisy stomach. For example, a person may have an allergy that causes mucus to drip from the nasal area and down the throat. You may swallow frequently, taking in some air along with the mucus you are swallowing; people with heartburn can swallow when the wash of stomach acid goes up into the esophagus. In the process of swallowing to move it back to the stomach, they may also swallow some air. Some people simply swallow more than others, often as part of a nervous condition; This causes more air to collect and make noise in the stomach.
Most people equate a rumbling stomach with hunger, which is correct, but the rumbling may not be the stomach after all. Unpleasant sounds can be swallowed air moving in the intestine. Also, foods that tend to produce more gas than others contribute to stomach and/or intestinal noise. Such foods include those that are high in fiber, including many types of fruits and vegetables. Beans are known to contribute to gas; Even juices and foods that contain sorbitol, a sweetener, can contribute to gas.