Normally speaking, due to the short nasal passages, cats will make moderate and even breathing sounds during normal times and when sleeping. This is normal; if your cat suddenly purrs louder, it is recommended that the breeder observe whether the cat has any symptoms. If there are signs of runny nose or cold, the breeder will give them cold medicine. Or the cat at home may be overweight, which may cause the purring to become louder and louder.