One of my cats since a kitten, has had the most unique purr. When he purrs it’s very “click.” As a kitten I brought him to the vet multiple times to have him screened for URI symptoms, as I didn’t think this was normal. Everytime he was given a clean bill of health. No abnormalities ever heard in lungs or in heart. When purring hard like this, you can also tell he breaths harder, as when he purrs his chest and stomach move. He is now 4yrs old, and within the last year had a health scare due to unrelated issues/symptoms. While at the vet, I opted to run every blood test on him I could, as well as had X-rays done to check his heart, lungs, and esophagus, all of which were completely normal. When relaxing he breaths completely normal, he plays a ton, is very physically active, great appetite, and all around normal behavior. Curious if anyone else’s cats do the same thing?