When we think of purring, we interpret it to mean a way our cat shows signs of contentment.
But scientists have other interpretions for what purring actually is and there are two schools of thought.
The first is a theory called the false vocal cord theory. It defines purring as originating from the cat's voice box and holds that the cat possesses a second pair of false vocal cords which produces the soft rumbling sounds. It views purring as heavy breathing or snoring.
The second theory is called the turbulent blood theory and holds that the cat's voice box has nothing to do with the purring. These scientists contend that the flow of blood through the cat's main veins into the heart is increased and turbulence is created and that is what causes the purring noise. The noise then goes through the animal's windpipe where it produces the purring sound.
Whatever is the true or correct explanation really has no merit to us pet owners. We know the real answer to be that purring signifies that our cats are happy and content which in turn causes us great delight knowing how well we take such good care of our cats!