How are internal body noises such as stomach rumbles produced, and why can we hear them?
鈥� There is always gas in the human gut, mostly hydrogen, nitrogen, carbon dioxide and methane. This gurgles about in a semi-liquid substrate. Vibrations in our gut generate audible sounds just like the skin of a drum does. Central-heating systems also produce gurgling noises, which are caused by trapped gases. The noises go away after 鈥渂leeding鈥� the radiators to release them. We bleed our stomach and bowels by burping and farting.
Hugh Hunt, Cambridge, UK
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