Researchers have just studied cats’ purring. So far it’s been a mystery. It has been found that cats have a type of cushion built into their vocal cords, hence that soothing and relaxing purr.
Mathilde Fontez, editor-in-chief of the science magazine Epsiloon, lifts the veil on a secret that fascinates us all: our cats’ purring. And we look at them now and listen to them differently.
franceinfo: A team of bioacoustics from the University of Vienna has just discovered how they purr…
Mathilde Fontez: It was a mystery. It’s true, it’s hard to believe: what is more familiar than a cat’s purring? It is not an exotic species, a strange insect hidden deep in the jungle. But until then, purring posed a problem for biologists.
Isn’t it produced by the vocal cords?
We thought that wasn’t possible. It’s all a question of frequencies: purring is a very serious sound, a low frequency sound: only 20 to 30 hertz – a man’s voice is 140 hertz. This is a type of sound not typically found in small animals. Normally only large animals with long vocal cords are able to produce such sounds. This is the case with elephants, for example.
Cats are rather small and their vocal cords are short, so they should only express themselves in high frequencies. That’s actually what they do when they meow. So there were hypotheses, such as the very rapid contraction of the larynx muscles, but no conclusion…
And today we know…
This team of bioacoustics discovered the cats’ trick: They discovered unusual masses of fibrous tissue embedded in the vocal cords. A kind of small pads with a diameter of 4 millimeters. These pads had been seen before, but no one had figured out their function.
They are the key to purring: they increase the density of the cat’s vocal cords. They put a certain amount of strain on the ropes. And that’s what allows them to produce this very deep sound. This also means that the cat’s purring, like meowing, is the same mechanism, a means of expression, and not just a muscle contraction.