Joseph Smith provided this description of the Savior: "We saw the Lord standing upon the breastwork of the pulpit, before us; and under his feet was a paved work of pure gold, in color like amber. His eyes were as a flame of fire; the hair of his head was white like the pure snow; his countenance shone above the brightness of the sun; and his voice was as the sound of the rushing of great waters, even the voice of Jehovah, saying: I am the first and the last; I am he who liveth, I am he who was slain; I am your advocate with the Father" (D&C 110:2-4).
In this instance Jesus' voice is described "as the sound of the rushing of great waters." A personal experience might elucidate this analogy.
When I was 11 I went on a 3 day backpacking trip down into the Grand Canyon. We started on the north rim of the canyon, which has an elevation of over 7000 feet above sea level. On top of the canyon the temperature is pleasant and cool. Down at the bottom of the canyon (over 4000 feet lower in elevation) it is hot with temperatures often over 100 degrees Fahrenheit in the summer. The hike is regarded as one of the most strenuous in the Grand Canyon. Water is only plentiful (with purification) at the bottom of the canyon at Thunder River itself. All other water has to be carried in. As you hike down the canyon you follow a switchback trail down the cliff. Your legs and knees start to ache from the jolts of walking down and down, sometimes going 2000 feet down in a mere 2.5 miles. As you near the bottom you are hot and tired. If you are not prepared you could end up out of water, lost, and delirious (like a small group of people we came across on our hike). But as we hiked along the prickly pear cactus-lined trail we started to hear something. There was a rumbling in the distance that slowly grew louder. The voice of the spring was a voice of thunder. What was quiet at first became the "sound of the rushing of great waters." Then suddenly we turned a corner and saw the waterfall. It was big, loud, and beautiful. 21 million gallons of water flow from the spring every day. It is an oasis in the desert, a refuge from the heat and dryness.
Now I do not know if the Savior's voice actually sounded like the rushing of great waters but Joseph Smith had to try to condense into the English language the experience of hearing the Lord Jesus Christ. Words cannot do justice to the experience of His voice or to Jesus' appearance but Joseph Smith used simile and metaphor to try to paint a picture for us. Eyes of fire, white hair, and a countenance brighter than the sun. Mortals have to be changed to enter into the fiery presence of the Lord. This fact is implied by the following description of the three Nephites who were promised that they would not die until Jesus' Second Coming: "And whether they were in the body or out of the body, they could not tell; for it did seem unto them like a transfiguration of them, that they were changed from this body of flesh into an immortal state, that they could behold the things of God" (3 Ne. 28:15). Their bodies were changed "like a transfiguration [so that] they could behold the things of God." We need to be changed, to be renewed and cleansed, to see the things of God.
That we need to be changed is more explicit in the book of Moses. "But now mine own eyes have beheld God; but not my natural, but my spiritual eyes, for my natural eyes could not have beheld; for I should have withered and died in his presence; but his glory was upon me; and I beheld his face, for I was transfigured before him" (Moses 1:11). Being in the presence of God is like being surrounded by fire, a fire of cleansing and purification. Without transfiguration, we cannot abide God's presence. We cannot withstand the intensity and heat. Joseph Smith said of his First Vision that the trees and plants surrounding him looked as if they were on fire. Like the burning bush Moses saw, the trees were not consumed because they had been changed to be able to withstand God's presence. Moses was commanded to remove his shoes in part as symbolism of the need to leave his old self behind - at least temporarily - in order that he might withstand the Lord's Shekhinah (the presence or dwelling or glory of the Lord): "And he said, Draw not nigh hither: put off thy shoes from off thy feet, for the place whereon thou standest is holy ground" (Exodus 3:5).