"Frequency of the Cat Purr" Did you know that cats heal bones? House cats may actually be contributing to our physical well-being. Exposure to the vibration of a cat purring between 20 and 50 Hz increases bone density, provides pain relief, heals tendons, etc. Russian athletes, for the Olympic team, are known for their increased performance when exposed to cats purring. They used a machine called "The Purr," tuned to the cat purring frequency of 50 Hz. Maybe that is why cats have 9 lives!