Ask A Scientist

How do cats purr? 

Asked by: Magdelana Jordan
School: Tioughnioga Riverside Academy
Grade: 6
Teacher: Mr. Johnson
Hobbies/Interests: Field hockey, basketball, Girl Scouts 
Career Interest: Dentist, teacher 

Answer from Shannon Miranda

Reader Services Coordinator at the Science Library

Research area: Resource sharing/interlibrary loan, services for students with disabilities.   Interests/hobbies: Traveling, animals, reading, knitting

Aren’t cats purr-fect? So, how do they purr?

The purring noise comes from the muscles of the larynx, which can be found inside of a cat’s throat. In support of this finding, cats with laryngeal paralysis cannot purr. The laryngeal muscles are responsible for the opening and closing of the glottis (the part of the larynx which holds the vocal cords), which results in a separation of the vocal chords. That is how the purring sound is made.

Studies have shown that the movement of the laryngeal muscles is signaled from a unique neural oscillator (oscillator means "to move back and forth.") The average frequency at which the muscles move to create this sound is approximately 25 Hertz, which means 25 beats per second. The average loudness of a cat purring is 84 decibels, which is equivalent to the sound of traffic from inside of a car. The purring sound comes from the mouth and nose of a cat. As a cat gets older, its purring stays the same. What is also unique is that a cat can breathe in and out and continue to purr, but can only meow when it breathes out. 

Now, onto why cats purr. It is believed that cats purr when they are happy or content. But, they also purr when they are scared, anxious or in pain. Many believe that when cats are in a more negative setting, purring helps them relax and cope with what is troubling them.

Lastly, do all cats in the Felidae (cat) family purr? No. The cats that live with us, domestic cats, do purr. Other cats in the cat family who purr are: cheetahs, Asian golden cats, black-footed cats, wild cats, Indian desert cats, jaguarundis, ocelots, tiger cats, margays, servals, Eurasian lynxes, bobcats, leopard cats, pumas and marbled cats. Big cats, like lions, leopards, jaguars and tigers, do not exhibit true purring. They can roar, and they make sort of a huffing sound between breathing in and out, just not as a continuous purr as other smaller cats do.

Here at the Science Library at Binghamton University, we have many scientific journals. One called the Journal of Zoology has an article that has been widely used to explain this very topic! 

Last Updated: 3/1/17