Another common cat noise is the purr. Cats purr when they are content and happy. The auditory frequency of the purr, around 25 cycles per second, is thought to have healing properties, and it almost certainly acts as an internal massage.

Purring is vital for the survival of newborn kittens. The little ones are welcomed into the world by the soft vibrations of their mother's purr. They are born deaf and blind, but they do feel vibrations. These sweet vibrations are perfect homing devices, guiding newborns to the protective warmth of their mom's body and to their first meals.

Kittens start communicating back to their mom and them siblings through purrs. They start purring when they are two days old. When kittens nurse, they cannot meow, so they show their contentment by purring.

Cat purring also keeps newborns safe from predators. Hungry predators are more likely to detect cries and other vocalization rather than the vibrations of purrs.