It is characterised by a high pitch and frequency. In the early stages of complete intestinal obstruction, episodes of bowel sounds are more frequent and can be particularly high-pitched. In more severe cases, air-over-water sounds or even metallic sounds can be heard, and high-pitched bowel sounds can be heard outside the abdomen without relying on a stethoscope. In late stages, the bowel begins to necrotize and the bowel sounds may disappear completely.