The frequency of purring is controlled by the brain. The whole mechanism is based on the vibration of the cat's diaphragm and larynx. The rhythm follows the breath. Cats purr on inhalation and exhalation in a consistent manner at a frequency between 25 and 150 hertz. Vocal cords do not move as in meowing, but only open and close. Research confirms that purring has healing properties. When a cat is injured or unwell, it purrs to heal itself. A broken cat's paw heals faster, much faster than dog's paw, for example.
Sound in the interval between 25 and 50 hertz has a positive effect on bone growth and fusion, relieves pain and reduces inflammation. It is the frequency of 25 hertz that is used in vibration therapy to accelerate recovery after injuries or operations.
So when a cat rubs against you and responds positively to touch and caress, it feels good and purrs at a low frequency - around 25 hertz - because it likes you and to instinctively reinforce itself.
Sitting with a purr on your lap has many advantages for us humans. Cat vibes have a calming effect because they reduce the secretion of the stress hormone, which in turn reduces the risk of heart and circulatory system problems and evens out pressure and breathing. If you have sore muscles, your muscles ache or you have a broken leg, do not refuse to stroke and caress your cat. ❤️