 Cats are surprisingly vocal animals, communicating with meows, trills, hisses, growls, yelps, and shrieks. But perhaps the most enchanting and mysterious noise they make is the purr. There's something relaxing, almost hypnotic, about this unique and frankly odd animal vocalization. But what does it mean? Purrs do more than simply calm down your cat, scientists also believe these vibrations can help heal injuries, repair and build muscles, and even act as a painkiller which might explain why injured or sick cats choose to expend valuable energy on purring.