purrs

Purrs are a low, continuous vibrating sound produced by some mammals, most notably domestic cats. The sound arises when a neural oscillator in the brain drives rapid, rhythmic contractions of the laryngeal muscles, causing the glottis to open and close repeatedly during breathing. Purring is most often heard during both inhalation and exhalation, with a typical frequency range around 25 to 150 hertz.

In domestic cats, purring commonly occurs when the animal is content, relaxed, or receiving affection, such as during petting, nursing, or resting. It can also be heard in other states, including distress, pain, or fear, which suggests purring may function as a self-soothing mechanism or as a flexible social signal.

The exact purpose of purring is not fully understood. Proposed roles include strengthening social bonds between mothers and kittens, communicating with other cats, and promoting self-soothing. Some theories propose physiological benefits from the vibrations, such as stimulation of tissue healing, reduction of swelling, or facilitation of bone growth; however, evidence for these health benefits is not definitive and remains a topic of research.

Purring is most strongly associated with domestic cats and has been observed in several other small to medium-sized felids, though not all can produce a true purr. In many larger felids and some wild relatives, similar sounds may occur but are not classified as true purring, and the mechanism may differ.

Overall, purring is a distinctive vocalization with unclear, multifaceted functions that likely include social communication, self-soothing, and potential physiological effects, varying across species and contexts.