Happiness and Satisfaction
Is there a more calming sound than the purring of a cat? Hardly. If you are sad, nothing is more comforting than petting a purring cat. It relaxes a person, makes us happy and peaceful. I still remember the first purring from each of my cats: Fox, who investigated his new home with loud purring, or Vincent, who when I went to visit his previous owners, came into the guest room, hopped up onto my bed and purred for hours.
I discovered that cats have very different personalities when the triplets came to live with us. The small but very courageous Donna came and sat on my lap and purred loudly and confidently already on her first day with us.
Turbo waited to see how his sister would behave. Once he saw that nothing bad happened to her, he took heart and came to me as well. As I petted him softly, he started to purr, too.
In contrast, Rocky was (and still is) very fearful and shy. He spent the first week in his new home in the fabric tunnel that we had purchased as a toy for the cats, emerging only when he was hungry or had to use the kitty litter. After a few weeks, he decided that we were no threat and made friends with us, and he started to feel more at home in our house. He blossomed into our number one cuddle cat. He purrs more frequently and louder than all the rest, and sometimes, when I come into a room where he is lying on a blanket, I can hear before I open the door that he is purring away to himself without any reason at all. Cats really do sometimes purr when they are alone.
The injured Vimsan purred as soon as I petted her for the first time, and although her purring is still very quiet, I often hear a soft buzzing, almost like regular, weak creaking sounds—but when you put your ear up to her body, you hear that she is really purring. Kompis purred at me for the first time when I fed him (he was probably really hungry, and he did not care at all that it was some strange woman, whom he had never seen before, who was giving him something to eat!). Even today, he purrs regularly and loudly when he follows me inside from the garden to get his breakfast or when he is lying on his favorite footstool or my husband’s lap and is being petted.
The first recordings of cat sounds that I ever recorded and investigated using phonetic methods were of our old cat Vincent. In the video, he is lying on a blanket on the couch purring. Therefore, I have a special relationship to the sound of purring.
Description of the Sound
Purring is a very low-pitched (often between 20 and 30 Hz), sustained, relatively quiet, fairly regular, humming sound. Cats often produce it for minutes at a time while breathing in as well as out. Most people know this typical cat sound very well and know that it is a sign of satisfaction. But cats do not purr only when they are happy or satisfied. They also purr when they are hungry, stressed, afraid or in pain—even when they are dying. Females purr while they give birth. Purring probably means something more like “I am no threat,” or “keep doing that,” than “I am happy.” It makes perfect sense.
Some say that the sound of a purring cat may have a healing quality for people. Both lower blood pressure and an antidepressant effect have been ascribed to it. Moreover, purring may be good for cats. It seems that it releases endorphins that help cats to calm themselves. However, to my knowledge, there are no scientific publications supporting these claims. Hopefully, future systematic studies will increase our knowledge of the effects of cat purring—on cats as well as on humans. Maybe purring is a meditative sound that cats can employ when they want to relax themselves or even pacify other cats.
Cats are born deaf and blind, but are able to perceive the vibrations of their mother’s purring. It is how they find the milk they need to live. It is possible that cats communicate with their young by purring because it is a very soft sound that is not easy for predators to hear.
Young cats often purr when they encounter adult cats, so as to signal that they accept that they are at the bottom of the social hierarchy and that they have only peaceful intentions. The older cat often answers with a purr in order to make it clear that the young do not have anything to fear from them.
Many wild cats purr as well. Among the best known may be the beautiful cheetah Caine, whose sounds were recorded by Dr. Robert Eklund in South Africa. You can find an example on my website in the category “Purr(ing),” under the keywords “Caine the purring cheetah.” Though there is a big difference in size between a cheetah and a house cat, they purr very similarly. The frequency usually lies between 18 and 25 Hz (so it is very deep) and the inhalation phase is roughly as long as the exhalation phase.
Research has determined that every kind of cat can either purr or roar, but never both. That lions, tigers, jaguars and leopards roar rather than purr probably has to do with the difference in the anatomy of their larynxes (voice boxes) to those of the purring cats. To be more precise, the degree of ossification in the hyoid bone beneath the tongue presents a plausible explanation for the fact that some cats purr and others roar. Roaring cats have an incompletely ossified hyoid bone, which enables them to roar but not to purr. All other cats have a completely ossified hyoid bone, which allows them to purr but not to roar.
One exception is the snow leopard, who appears to be able to purr despite having an incompletely ossified hyoid bone.
Some cats purr a little louder during inhalation, others during exhalation. Adult cats seem to purr the most when they are fed or petted. Some also purr when they are alone in their favorite place, like our Rocky, who often purrs for hours at a time when he is lying in his basket on the desk. Other cats start to purr when they arrive someplace new and want to investigate if it is safe. That is how it was with my black-and-white Fox, who walked around my apartment purring and getting to know everything the first time he was there.
If your cat does not purr, it is possible that they were separated from their mother too early and never learned to make the sound. It is also possible that they simply purr very quietly, so that we humans can hardly perceive it.
Tip: If you are having difficulties hearing your cat purring, try to make them lie down on your pillow next to your head and pet them until they start to purr. Even if the purring is very quiet, the pillow will act as a kind of resonance box and amplify the vibrations so that you will be able to hear—or feel—them better. The larynx, or even the whole body, vibrates when a cat purrs.
Anyone who is near a purring cat can hear that the sound is loudest at the front of the mouth, which indicates that it is produced in the larynx, or, to be more precise, with the vocalis muscle in the vocal folds (vocal cords), which produce the vibrations through a rapid twitching or contracting. Dr. Robert Eklund, with whom I conducted the research project “Melody in Human–Cat Communication,” has investigated the anatomy of the larynx of many cats, including wild cats, but even he can only speculate when asked how cats actually purr.
One possible means of investigating the articulation (position or movement of the mouth) of purring cats with phonetic methods would be to employ an ultrasound or MRI recording of the larynx, with which one could see which organs vibrate and how the vocal folds move. But how can you convince a cat to purr when it is in a strange room with strange people, tied up in a scary, loud device and then shoved into a tube? Or when a strange vet sticks a hard ultrasound sensor firmly against their shaved throat, which has been coated in gel? They will hardly be in the mood to purr!
Not all purring sounds are the same. The same cat can even produce very different purrs depending on emotional state, mood or situation. A study in England concluded that cats have developed a special loud kind of purring or a “cry embedded within the purr” that they employ when they want attention or something to eat from us humans (McComb, Taylor, Wilson & Charlton, 2009).
Cats can also combine their purring with other sounds. A cheerful and hungry cat can meow, trill and purr in sequence—usually in anticipation of a treat they are about to receive. Many cats purr and trill when they want to cuddle with their humans. A sleeping cat can combine purring with snoring.
Rocky the super purrer has a very calming purr, which he produces by slow inhalations and exhalations. Donna usually purrs a little more quickly, especially when she’s happy about something, such as a treat or being able to crawl into my cardigan while I’m sitting at my desk. Turbo also often purrs when he is happy about something. He likes to combine meowing and trilling with purring, and sometimes his purring, which is usually so meditative, can even turn into a very agitated noise.
Kompis also likes to purr. His purr is often very deep and loud. He mostly purrs when we give him something to eat, pet him or when he is in his favorite place—the footstool with the soft blanket in the hall.
When I read about the English study with the title “The Cry Embedded within the Purr,” I was not entirely convinced that such a purring cry or call really exists, as I had never observed it in my own cats. Can all cats really produce such a sound? I started to examine all the purring sounds that I had recorded of my own and of other cats with my phonetic ears, and although I have not been able to make out a call or a cry in the purrs of my cats, I did find that there are many varieties of purring and that cats can pep up their purrs with other sounds. Donna often trill-purrs or squeak-purrs, which are truly the cutest cat sounds that I have ever heard. She kneads around on my lap and purrs, trills and squeaks in ever quicker succession until the sounds are all mixed up—it is irresistibly sweet!
Turbo sometimes purrs in his sleep. As he also often snores, he sometimes ends up producing a combination of snoring and purring, which is also very cute! Have you also heard your cats make unusual combinations of purring and other sounds?
TIP: At the end of the book you will find links to sound files of purring cats on the website. Maybe you will find some similarities to the purring of your own cats! See the appendix.
Corresponding Body Language
Because purring is usually a sign of well-being, most people have a mental image of a cat curled up happily on the lap of its human. Indeed, the typical purring situation is when our furry friends are comfortable in their favorite place, whether it is the lap of their human, in a basket or maybe on a soft blanket. It is not uncommon for them to make a turning motion, often kneading with their paws in the process, before lying down. Kittens purr while they are at their mother’s teat so as to stimulate the production of milk. Many cats also purr sitting, standing or walking. Eye contact with humans and ears pointed forward often go with purring. The tail is usually still, and often raised, and its tip can be curled like a question mark. This is a sign of affection and tenderness. It is even more intimate if a cat blinks or closes its eyes altogether while it purrs. If your cat blinks at you like that it probably means “I trust you from the bottom of my heart.”
Phonetic Categorization (Sound Type, Melody)
Purring is usually produced with a closed mouth, during inhalation as well as exhalation. The air is mainly inhaled and expelled through the nose, so purring can be classified as a nasal sound; it is, however, probably mostly a voiceless sound. Purring has no clear melody, unless it is mixed with trilling or meowing. It is also typical of purring that it is very quiet and often lasts for a long time (often several minutes). That is possible because the cat does not need to take a break between each purr in order to inhale. Instead, the sound can be produced while the cat inhales as well as while it exhales. The inhalation lasts somewhere between half a second and one second, and then quickly turns into the exhalation, which lasts about as long. In some cats, one of the phases can be significantly longer, louder and deeper in frequency.
Phonetic Description and Transcription
Purring is a soft, very deep, probably mostly voiceless (but regularly vibrating) consonant sound completely without vowels. It most closely resembles an airy, nasal trill like an [ʀ̃] or [r̃] often combined with a soft [h] consonant. Every inhalation and exhalation phase has a length (duration) of between one half and one second. The transition between phases is short and rapid.
Moelk transcribed purring as [‚hrn-rhn-‘hrn-rhn…]. With the help of the International Phonetic Alphabet, I would write this as roughly [↓hːr˜-↑r˜ːh-↓hːr˜-↑r˜ːh] or [↓hːʀ˜-↑ʀ˜ːh-↓hːʀ˜-↑ʀ˜ːh]. Purring can be combined or even mixed with other sounds, frequently trilling or meowing.
TIP: The phonetic symbols are described in detail in Tables 3, 4 and 5 at the end of the book.
Voice and Melody
Purring is mostly voiceless, although it is probably produced using muscles in the vocal folds. It is a regular sound, but so low-pitched and deep that one can hear the pulsating of the larynx as it vibrates. It sounds almost like a softly rattling chain to the human ear. The very deep vibrations are more or less monotone, though there is a difference in the frequency of the inhalation and of the exhalation in some animals. Mixed purr combinations (with trilling and meowing) can be voiced.