The larynx, or ‘voice box,’ of domestic cats (Felis silvestris catus) can produce purring-like sounds without neural input, according to new research led by the University of Vienna.
Most mammals produce vocal sounds according to the myoelastic-aerodynamic (MEAD) principle, through self-sustaining oscillation of laryngeal tissues. In contrast, domestic cats (Felis silvestris catus) have long been believed to produce their low-frequency purr vocalizations through a radically different mechanism involving active muscle contractions. Herbst et al. show that low-frequency phonation in the purring range (20-30 Hz) can readily be elicited in the excised larynges of domestic cats in the absence of muscular contraction or neural input. Image credit: Natali Anderson.
Cats are vocal creatures: they meow, screech, and purr.
From a voice production point of view, the meows and the screeches are not special.
Their sound is generated in the larynx just like vocalization in humans and many other mammals.
In contrast, cat purrs were long believed to be exceptional.
About five decades ago, studies suggested that the purrs are produced by a special mechanism — through cyclical contraction and relaxation of the muscles in the vocal folds within the larynx, requiring constant neural input and control from the brain.
In the new study, University of Vienna researcher Christian Herbst and colleagues demonstrated that these cyclic muscle contractions are not needed to generate cat purrs.
The data from a controlled laboratory experiment show that the domestic cat larynx can produce impressively low-pitched sounds at purring frequencies without any cyclical neural input or repetitive muscle contractions being needed.
The observed sound production mechanism is strikingly similar to human ‘creaky voice’ or ‘vocal fry.’
“Anatomical investigations revealed a unique ‘pad’ within the cats’ vocal folds that may explain how such a small animal, weighing only a few kilograms, can regularly produce sounds at those incredibly low frequencies (20-30 Hz, or cycles per second) — far below even than lowest bass sounds produced by human voices,” Dr. Herbst said.
“Our findings — while not constituting an outright falsification of the previous theory — are a clear indicator that the current understanding of cat purring is incomplete, and warrants further research.”
The study was published in the journal Current Biology.
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Christian T. Herbst et al. Domestic cat larynges can produce purring frequencies without neural input. Current Biology, published online October 3, 2023; doi: 10.1016/j.cub.2023.09.014
