What do guinea pig purring noises sound like?

It sounds like a cats purr! its great to hear guinea pigs purr, it meens they love you. please do not confuse it with growling. . . guinea pigs will not growl. Hope this helped i hope your guinea pigs purring for you. i have 2 that purr non stop! one purrs if i pet it, and the other purrs if it has food and i stroke him.