Cheetahs do not roar; instead, they meow and purr.
The sounds made by a cheetah are not frightening. Cheetahs sound more like a house cat than a lion, which is noted for their fierce roar. They purr and meow. They also chirp and create churring noises. Listen to some of the Toronto Zoo's noisy cheetahs. Lions, tigers, leopards, and jaguars are the four roaring great cats. They can generate their threatening noises because their voice box has a ligament rather than the epihyal bone. Lower noises are produced as the ligament stretches. Cheetahs have a fixed voice box and vocal cords that are split. It permits them to purr but limits the noises they may produce, similar to "little cats."
In 1931, a scientist decided to undertake an experiment in which he raised a monkey as if it were a person.