How do cats purr?
Research has shown that cats' muscles move the vocal cords and, as they breathe in and out, air hits the vibrating muscles, which creates the purring sound.
You probably didn't know that cats that purr can't roar, and cats that roar can't purr, because of the small bone found inside the vocal cords, which in roaring cats, is a flexible bone.
This allows big cats to make a deep, roaring sound but in domestic cats is completely hardened and only allows air vibrations while exhaling and inhaling.
Researchers have also recently identified a new purr called the "solicitation purr",
which alters the normal purr into a more urgent "cry-like" sound, which is similar to that of a crying baby, so that we instinctively want to help.