I have heard them hiss and make grunting sounds when we visited Florida, so yes, they do. read more
Alligators can make too main loud noises. They are capable of a loud hiss, usually this is a defensive warning, if you press it further it will either attack or run. The fun one though is the bellow. read more
A.Sanichar has a video with the boom recorded — ignore the tenor “faaaaaa” that sounds human, that's a recording artifact. The low boom and the water disturbance is the sound of a bull gator calling a female. Alligators boom in B flat, and booming choruses can be induced by tuba players, sonic booms, and large aircraft. read more