All members of the cat family (known as Felidae) including domestic cats, tigers, leopards, lions, cheetahs, jaguars and panthers purr. Purring generally means a tonal buzzing, which alternates between pulmonic egressive and ingressive airstream (and can go on for minutes). While the bigger cats do so when breathing out, domestic cats purr when they inhale and exhale.
As most of us probably know, cats purr when they are happy. You can hear them making that particular sound when they’re patted by their owners, or are being fed, or are nursing their progenies. However, there can be different reasons for different cats for doing it. When they feel threatened or are in pain, they rely on their comfort mechanism to soothe their minds. Cats also purr when they are anxious, which again attests purring as being an instant relief system or a form of self-healing. Some cats purr when they’re giving birth. They do it when they want to be fed. Such purr, however, comes with a variation on the usual purr and may sound like a cry similar to a human infant’s.
Scientifically speaking, a cat’s brain has a repetitive neural oscillator, which is responsible for sending messages to the laryngeal muscles. When it does so, the laryngeal muscles twitch at a rate of 25 to 150 vibrations per second. This vibration allows the vocal cords to separate to produce a purr upon exhaling and inhaling. Moreover, purring has its therapeutic benefits like pain relief, wound healing and bone growth.