Researchers have unravelled the mystery behind the distinctive low-pitched purr of cats, revealing that it involves "purring pads" in the vocal cords. The international team, led by scientists from the University of Vienna, challenges the conventional belief that active muscle contractions cause purring. Instead, they propose that purring is a passive aerodynamic behaviour triggered by an initiating brain signal. The "purring pads," composed of collagen and elastin fibres in the vocal cord's connective tissues, increase density and slow down vibrations, producing the characteristic rumble.
While scientists had previously discovered these structures in domestic cats, their role in purring was not explored. To investigate, the researchers removed larynges from eight deceased domestic cats, applying warm, humidified air without muscle contractions or neural input. The vocal cords produced a purring sound through self-sustained oscillations at frequencies typical of a domestic cat purring, ranging from 25 to 30 Hz.
While the study does not entirely reject the active muscle contraction hypothesis, it emphasises the potential role of connective tissue structures as the primary driver of purring. Further research is needed to validate this in living cats.
The reason cats purr remains unknown, with theories suggesting it indicates contentment, encourages interaction, and may serve as a healing mechanism. Understanding the mechanics of purring could provide new insights into feline health and well-being, potentially leading to the development of technologies that mimic purring sounds for calming devices or innovative treatments for pain and anxiety in cats.