The sound of a cat purring is usually made when it is in an environment where it feels comfortable and trusting, because it is very relaxed and in a good mood. Generally, the cat will make this sound when the owner strokes the cat's head and chin. This sound is made by the muscles in the throat opening and closing when breathing.

There is also a situation where the cat is very angry, and out of an offensive or defensive posture, it makes a purring sound to deter the other party. It is best for the owner to immediately take the cat away from strange dogs and other cats, or stop doing things that the cat does not like, otherwise the cat is likely to attack.