Now We Know

High speed imaging of a cat glottisFollowing over a century of investigation we now know how cats purr, well probably.

The short version is that they took larynzxes of euthanized cats, with owners' permission, and blew air through them at various speeds, and managed to recreate the phenomenon.

We still have no clue as to why cats purr, though.

I loves our furry enigmas:

There are few things more gratifying to cat lovers than a contentedly purring feline. But the precise mechanisms by which kitties produce those pleasant, low-frequency rumblings has been a matter of some debate among scientists. Now a team of Austrian scientists has determined that connective tissues embedded in cats' vocal cords play a crucial role in this ability, according to a new paper published in the journal Current Biology. The authors argue that their findings call for a reassessment of the current prevailing hypothesis about how cats purr.

Purring is mostly exclusive to cats, although certain other species can produce purr-like sounds, including raccoons, mongooses, kangaroos, badgers, rabbits, and guinea pigs. And cats are usually divided into those that purr (Felinae) and those that roar (Pantherinae); no cat species can do both. The latter category includes lions, tigers, jaguars, and leopards, and scientists have suggested that the roaring capability is due to an incompletely ossified hyoid bone in the larynx. "Purrers," by contrast, have a completely ossified hyoid, although the purring snow leopard is a rare exception.

We know the fundamental frequency at which cats purr—between 20 to 30 vibrations per second, although purrs can go up to about 150 Hz—but that is lower than expected based on vocal cord anatomy. As a general rule, larger animals have longer vocal cords and thus create lower-frequency sounds. But cats are relatively small, typically weighing on the order of a few kilograms, and their vocal cords are also relatively short. Hence the curiosity about how they produce such low-frequency purrs.

There are few things more gratifying to cat lovers than a contentedly purring feline. But the precise mechanisms by which kitties produce those pleasant, low-frequency rumblings has been a matter of some debate among scientists. Now a team of Austrian scientists has determined that connective tissues embedded in cats' vocal cords play a crucial role in this ability, according to a new paper published in the journal Current Biology. The authors argue that their findings call for a reassessment of the current prevailing hypothesis about how cats purr.

Purring is mostly exclusive to cats, although certain other species can produce purr-like sounds, including raccoons, mongooses, kangaroos, badgers, rabbits, and guinea pigs. And cats are usually divided into those that purr (Felinae) and those that roar (Pantherinae); no cat species can do both. The latter category includes lions, tigers, jaguars, and leopards, and scientists have suggested that the roaring capability is due to an incompletely ossified hyoid bone in the larynx. "Purrers," by contrast, have a completely ossified hyoid, although the purring snow leopard is a rare exception.

We know the fundamental frequency at which cats purr—between 20 to 30 vibrations per second, although purrs can go up to about 150 Hz—but that is lower than expected based on vocal cord anatomy. As a general rule, larger animals have longer vocal cords and thus create lower-frequency sounds. But cats are relatively small, typically weighing on the order of a few kilograms, and their vocal cords are also relatively short. Hence the curiosity about how they produce such low-frequency purrs.

………

The authors successfully produced purring sounds in all eight of the excised larynxes when air was pumped through them, with no need for muscle contractions—given that all the adjacent muscles had been removed when excising the larynxes. So what was driving the purrs? They concluded that it was the presence of connective tissue embedded in the vocal cords, which also served to lower the frequency of the purring sounds. In other words, cats rely on the same MEAD-based mechanisms to purr as other mammals do for their vocalizations.

The prior theory was that cats used specialized muscular contractions to create these sounds, but it appears to be a normal vocalization where the vocal chords are tightened or loosened like a guitar string.

The reason that cats can purr is because of the cartilage in their vocal chords.

It's kind of the difference between between a yew English longbow and a composite Mongol bow, which is made out of a combination of horn, sinew, and bamboo along with glue.