A British pet kitty is believed to have the loudest purr in the world - as loud as a lawnmower! Most cats purr at around 25 decibels but, according to London's Telegraph, 12-year-old Smokey's powerful purrs average an amazing 80 decibels. Measured close-up, her purrs reach an incredible 92 decibels, equivalent to the noise of a lawnmower, hair dryer or a Boeing 737 coming into land.