Purr-fect pets!

A cat’s purr has to be one of the most comforting sounds in the world. The constancy of that low, rhythmic vocalisation resonating in your ears says that everything is alright with the world – or even if it isn’t, it soon will be. There is still a lot we don’t know about how and why cats purr, but what has been discovered is quite illuminating.

Cats purr during inhalation and exhalation, probably through the alternate use of the laryngeal (throat) and diaphragmatic muscles.

We usually associate cats purring with moods of contentment and happiness, but a cat will also purr when it is wounded, startled, or distressed. It has been theorised that this is a way for the cat to calm itself down, or possibly to show submissiveness in the face of an external threat.

All domestic cats are born with the ability to purr. Some big cats such as pumas, cheetahs and leopards exhibit a purr-like sound, but are only able to do this on exhalation.

The measurable range of a cat’s purr is between 25 and 150 Hertz (Hz).

There are even podcasts and CDs that have been released featuring cats purring, as a method of relaxation akin to meditation. These are made on the basis of fascinating studies done by The Fauna Communications Research Institute in North Carolina, which point to evidence that purring is a natural healing mechanism that aids in strengthening bones and organs through vibration. The curative quality of purring has also been linked to the myth of cats possessing nine lives, due to their relative lack of orthopaedic disease and the speed at which bone fractures and similar injuries mend.
Research is still being done on the matter, but the potential for applications in sound therapy and pain relief for humans is exciting.

A ‘low-range’ purr at 26Hz is close to the frequency of a running diesel engine, which explains why your purring pet may sound just like the car!

Sources and Further Reading
http://www.bksv.com/NewsEvents/BruelKjaerMagazine/OtherArticles/TheCatsPurrMystery.aspx
http://cats.about.com/cs/catmanagement101/a/why_cats_purr.htm