Purring

Biologists have been a little more successful in understanding how cats purr. In February 1991, physiologists Dawn Frazer and David A. Rice of Tulane University in New Orleans, La., and G. Peters of the Alexander Koenig Museum in Germany reported that purring consists of low frequency sound produced by vibrations of the cat's larynx (voice box) during inhaling and exhaling. These researchers recorded the sounds through instruments that they placed on various parts of the cat's body. They found that the sounds were not linked to the sounds of the cat's breathing pattern, which is why purring is continuous. Purring may in fact occur simultaneously with other vocalizations.

Scientists do not know the purpose of purring, however, especially as it might have served the cat's wild ancestor. Purring appears to be a sign of contentment, yet even cats that are ill and in discomfort may purr. Cat owners recognize that purring occurs when cats are around people, but the presence of people is not essential for purring. Cats may purr during mating —and kittens, while nursing. But cats of any age do not purr while they are sleeping.