The only big cat that doesn't roar is a cheetah

Every other big cat has a fierce and load roar, except for cheetahs. Instead of roaring, cheetah's meow and purr just like you would expect a regular domesticated house cat would. This is no surprise when you consider that the cheetah's anatomy is remarkably similar to that of a small cat despite being many times larger. A cheetah's voice box is fixed and therefore its vocal cords vibrate as they breathe, enabling them to meow and purr but removing their ability to roar like their other big cat cousins.