A purring cat on your lap seems the picture of contentment. But cats also purr at the vet, when giving birth and when injured. Purring is more than a “happy” sound.
How the sound is made
Muscles in the cat’s larynx (voice box) twitch rapidly, opening and closing the gap between the vocal folds. Air passing through on both the in-breath and the out-breath makes the vibration — which is why purring sounds continuous. The rhythm comes from a “neural oscillator” in the brain, and the frequency is typically around 25–150 vibrations per second.
Why cats purr
- Contentment and social bonding — kittens purr while nursing, and the mother purrs back.
- Asking for something: researchers found some cats mix a higher-pitched cry into a “solicitation purr” when they want food — one humans find hard to ignore.
- Self-soothing when stressed, frightened or in pain.
The healing theory
Some researchers have suggested that vibrations in the purring frequency range might help bone and tissue repair, since similar frequencies are used in some physical therapy. It is an interesting idea, but it hasn’t been proven for cats.
Big cats
Cheetahs, pumas and other small-to-medium wild cats purr. Lions and tigers generally roar instead — the structure of their voice box allows roaring but not the continuous purr of a house cat.
More animal oddities in Animals & Nature facts.
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