In Ancient Mesopotamian Religion/Mythology, Humbaba was a terrifying giant who was sent by Enlil (the god of air, wind and storms) to be the guardian of the Cedar Forest. The Cedar Forest was the realm of the Mesopotamian Gods and where no mortal or normal human being was allowed to enter. He was sent there to protect the forest by terrifying any man that dared enter the forest by using his size and god-like feature to be almost unstoppable when at the right moment. He has been described as having the look of death, a roar/voice that booms like thunder and his breath is fire. He's also able to hear a hundred leagues (miles) away. And his facial features can be altered to terrify even the strongest and bravest men, such as Gilgamesh. But Humbaba is not the only with some these traits that are used to show their true power. "The Balrog" from the Lord of the Rings movie is a perfect example to connect Humbaba, a giant beast that protects the Cedar Forest, to The Balrog, one of many servants of Morgoth who are described as tall and terrifying with the ability to surround themselves in fire, darkness, and shadow. Both creature, though in different worlds, connect in ways that make it seem that they'd cross path sometime down the road in their lives.
In the story of Gilgamesh, Humbaba can easily be recognized by the sound and intensity of his roar and voice. In the Lord of the Rings series, a Balrog's shout/roar is one of its most powerful characteristics and most terrifying characteristics as well. Humbaba was assigned to be the protector of the Cedar Forest, and to do this he'd need traits or characteristics to terrify any man that would dare enter the forest for any reason or to alter the forest in any way. So having Humbaba having a voice and roar so loud that it is described as thunder isn't surprising being as his size and image is superhuman and maybe even god-like. This characteristic alone has been talked about being something that brave warriors even are stopped dead in their tracks by the sound of his roar.