The peaceful rumble of purring is a familiar sound to cat parents, but many feline aficionados know very little about their cat’s anatomy. And that’s OK! Most cat parents won’t need to know all the details, like memorizing every muscle in their cat’s body, but it can be fascinating to learn about the anatomical functions that make a cat unique, like purring.
Plenty of folks know that purring can be the sound of a happy cat, but how do cats purr? Is it a vocalization like meowing, or something else altogether? Let’s learn more about how cats purr and why they make this unique sound. You’ll be an expert in purring in no time.
How do cats purr?
For a long time, scientists believed that purring was a type of vocalization, similar to meowing. They hypothesized that cats used their muscles to contract and relax their vocal cords at a massive speed: up to 30 times per second. However, recent studies have proved that they don’t need to contract muscles to make this sound.
A study published in Current Biology found that neither muscles nor brain signals are required to produce a purr in cats. Researchers examined the larynges, or vocal cords, of eight domestic cats that had passed away due to terminal illness and whose bodies were donated to science. When air was forced through the vocal cords, the resulting sound was a purr at the same frequency heard in living cats.
So what does this mean? These findings prove that purring isn’t a vocalization like previously thought. Instead, it seems like a central nervous system response that cats don’t actively control. The unconscious brain controls the nervous system, tells the vocal cords to press together, and then the brain’s job is done. From there, all that’s needed is air flowing through the vocal cords.
This phenomenon is known as flow-induced self-sustained oscillation, and it occurs in various animals, including humans. In people, it manifests as a creaky sound called “vocal fry,” while in cats, it results in purring. What makes purring particularly unique in felines is that the sound is produced during both inhalation and exhalation, allowing them to purr continuously.
Low-frequency sounds
One reason cat purrs are unique is their low frequency. Cats typically purr at around 20-30 Hertz, which is at the very low end of the range that human ears can detect. This is odd because cats have such small vocal cords compared to much larger animals like elephants. Typically, longer vocal cords produce lower sounds, but cats seem to be the exception to this rule. How fascinating!
The researchers who studied the larynges of the cats who had passed away discovered a unique set of “pads” on the cats’ vocal cords that may be responsible for this anomaly. They hypothesize that the pads slow the vibration of the vocal cords, creating the low-frequency purring sound we all know and love.
Why purring is hard to evaluate
Feline researchers have had limited opportunities to study purring, primarily because it is difficult to observe in a controlled environment. Purring typically occurs when a cat is content, but cats are unlikely to feel relaxed in a research lab equipped with cameras and probes inserted into their throats. Cats also can’t purr on command, nor are they likely to purr while lying still for an MRI, so research remains limited.
Why do cats purr?
There may be some mystery surrounding how cats purr, but it can be easy to tell why cats purr. Often, purring is a sign of contentment or relaxation, but other times, they purr when they’re injured or in pain. Why is this?
Some researchers have found that the frequency and vibrations of a cat’s purr may have healing and anti-inflammatory properties. Cats could purr to heal themselves! It doesn’t work like magic or happen overnight, but this can be a helpful tool that cats use when they’re injured or sick.
Even so, cats aren’t the only ones to benefit from their purrs. These low-frequency vibrations can lower stress, lower blood pressure, and could even promote wound healing in people, too. If your cat has ever lain on top of you and purred while you were sick in bed, they may have been trying to help you feel better in their own special way.
There are so many reasons to love and appreciate a cat’s purr, so give yourself a pat on the back if you have a happy cat on your hands. And enjoy those peaceful purrs!
