The book of Revelation begins with "the Revelation of Jesus Christ, which God gave Him to show" (Rev 1:1). It was the "testimony of Jesus Christ" (:2) and sent to John "who testified to the word of God" (:2). God had appeared to them in a "pillar of fire" (Ex 13:21) and "thick cloud" (19:9) which was to "give them light" (13:21) and so that they would "believe" (19:9). At Mt. Sinai God appeared with "thunder and lightning flashes . . . and a very loud trumpet sound" (19:16) so the "people may hear" (:9). The Lord spoke to Moses, Aaron and Miriam (Nu 12:4) and they "came out" (:4) to the tent of meeting. Then God addressed Aaron and Miriam about speaking against Moses. They should have been more careful because when God speaks revealing himself you should pay attention.
How is it that you can hear and understand God? God had said, "'Let Us make man in Our image'" (Ge 1:26). "In the image of God He made man" (9:6). Being in the image does not mean having been cloned. It means "'according to Our likeness'" (1:26) as James states that we are men "who have been made in the likeness of God" (Jas 3:9). How it functions depends on God's sovereign purpose. "The Lord appeared to [Moses] in a blazing fire from the midst of a bush" (Ex 3:2). When Moses decided to investigate "the Lord saw that he turned aside" (:4) and spoke to him. If we are open to God he will reveal what he desires. Moses' situation was special because God said, "'With him I speak mouth to mouth, even openly, and not in dark sayings, and he beholds the form of the Lord'" (Nu 12:8). As Christians we "put on the new self, which in the likeness of God has been created" (Eph 4:24) and "is being renewed to a true knowledge according to the image of the One who created him" (Col 3:10). God said through Jeremiah that "'you will call upon Me and come and pray to Me, and I will listen to you. You will seek Me and find Me when you search for Me with all your heart'" (Jer 29:11). There is a general revelation available from nature and the works of God and special revelation through scripture (the Living Word) and subjective experience which lines up with God's word. "We know that the Son of God has come, and has given us understanding so that we may know Him who is true . . . the true God and eternal life" (1Jn 5:20).