It sounds like your cat’s purring is on autopilot. Researchers have finally found the key to the characteristic sound of these fluffy lumps found in the soft cushions of cats’ vocal cords. Scientists are pondering how cats achieve their characteristic low purr; because low-frequency sounds are generally made by larger animals with longer vocal cords.
These “humming pads” of connective tissue embedded in the vocal cords apparently increase the intensity, causing them to vibrate more slowly and creating a hum that brings joy to their humans.
An international team led by voice expert Christian Herbst from the University of Vienna in Austria says their research challenges the widely held belief that active muscle contractions are the cause of purring. Instead, scientists believe purring may be a passive streamlined behavior that continues automatically after the brain sends an initial signal.
“These low-frequency vibrations of the vocal cords involve a special vocal mode with an unusually long off-ratio, reminiscent of the ‘vocal water’ register in humans,” the researchers wrote in their published paper.
When we speak with our voice, we vibrate the vocal cords at a very low frequency, producing a low, high-pitched sound that is sometimes described as a “humming” or “creaky” sound. In addition to the thickness of the hole and the level of tension of the vocal cords, the air flow through them also plays an important role.
Purring pads work in a similar way, using the same mechanisms that normally produce higher-frequency sounds like meows, allowing little cats to purr even though their vocal cords are much shorter than ours.
Collagen and elastin fibers in the connective tissues of the vocal cords are arranged in structures that suppress the high frequencies of sounds, such as those of growling cats.
These structures, which are up to 4 millimeters in diameter, have been found in domestic cats before, but their role in purring has not been investigated. To find out, Herbst and his colleagues removed the larynxes containing the vocal cords of eight deceased domestic cats. They then squeezed the vocal cords together and blew warm, moist air into them.
Without any muscle contraction or neural activity, all eight larynxes produced a purring sound as a result of self-sustained vocal fold oscillations at frequencies in the purring range of a domestic cat (25 to 30 Hz). This surprising discovery shows that muscle contraction is not necessary for purring. Connective tissue structures may be the main driving force, but this will need to be proven by measuring the process in living cats, which is somewhat more difficult.
“Although our data do not completely reject the hypothesis that active muscle contraction causes purring, they do show that the cat’s larynx can readily produce purring sounds with a fundamental frequency of 25 to 30 Hz without neural input or muscle contraction,” the team wrote.
ReasonFrom where cats’ purring remains a mystery. Some theories suggest that purring indicates pleasure and encourages greater human interaction. Research also suggests that purring may be a healing mechanism. The research could lead to new insights into the role of purring in the health and well-being of cats. This could help scientists develop new technologies, such as ones that mimic purring sounds, calming devices for cats, and even new treatments for pain and anxiety.
Source: Port Altele
