There is nothing as intimidating or awe-inspiring as the most famous Kaiju’s roar. Though fictional, this is one of the things that defines him other than his massive size. But there are problems were physics is concerned. Sound is generated by the larynx in one of two ways: either purring mode or flow-driven mode. Purring mode depends on how quickly the vocal folds or vocal cords contract and vibrate. Flow-driven mode depends on how passing air vibrates those folds.
The sound produced in flow-driven mode depends on the size of the larynx. The larger the larynx, and hence the vocal folds, the lower the sound. Godzilla is so large, his roar would be in the infrasonic range; below the range of human hearing. Purring mode suffers from no such limitation. Could the King of Monsters actually be purring? Read my MoviePilot article to learn more.