I don't think anyone knows for sure but there are a couple theories on the subject. Some think it's due to a vibration of the soft palate because of increased blood flow. Then there's the reasoning that it's because nerve activation in the voice box.
I have no clue how they do it, but it sounds awesome!!! I love it when my babies purrr. It lets me know that they are content and happy. And they usually fall asleep soon after they begin purring! They are soooo cute:tounge2: I love my furbabies!
Scientists haven't been able to determine the source of the cat's purr, since in order to look inside the cat, the cat is in no condition to purr. It has been noted that they don't purr, just when they're contented: females purr while giving birth. I don't know how cats feel but the last thing that I felt, at that time, was contentment!
I've given up wondering the how and why of purring - I'm just glad that they do! When I have a migraine, purring is the only sound that does not hurt. Peanut, who I had for 14 years, always came and snuggled up, when the demon headaches hit and stayed by me, until I felt better. He was the best doctor that I ever had.
I have a little nurse, too. Ophelia always knows when we aren't feeling well and will give us snuggles and purrs. Even when she was really little and wouldn't hardly let us touch her, she did this. I got really sick and she didn't leave the bed (except to eat and use the litter box) for three days. Such a sweet girl!
Fifteen years ago, my husband, Russ, got walking pneumonia. I parked him on the couch, with an electric blanket. Feisty, our grande dame, plunked down on top of him and, except for food and litter box runs, she didn't get off, for three days. The following year, on the night that Russ died, she was on his lap, when the stroke hit. Russ was sitting on the side of the bed, Scotch and soda in one hand, Cuban cigar in the other, me in the bed and Feisty on his lap. He never felt a thing. What a way, to go, surrounded by the things that make you happy.