John hears a voice and turns to see it (Revelation 1:10, 12). C.E. Douglas (The Last Word in Prophecy, 149-51) observes that this picks up on a rich vein of biblical phonology.

Ezekiel heard a voice above the firmament, and what he saw was a human figure glowing like hot metal and a voice sending him to preach (Ezekiel 1-2). Israel never saw a figure on Sinai; not even Moses did. But both Israel and Moses “saw” a voice (Deuteronomy 4:12; 7:11).

John the Baptist comes as a Voice in the wilderness, and in the gospels we occasionally hear the Voice of the Father from heaven.

It all goes back, as everything does, to Eden: “In the duplicated account of creation at the beginning of the Old Testament first God speaks and the Law and Order of the universe come into being (Gen. 1). Then in the world that he has made the Place of Safety (Eden) is established for all eternity and administered by the Voice of Jahveh (Gen. 3:8).” This is the same Voice that John sees, the one who promises “the tree of life which is in the midst of the Paradise of God” (Revelation 2:7).

The Voice is a trumpet, announcing the “beginning of the eternal Year of Release,” going out to the “Seven Cities of Mankind to assemble in the valley of decision (Joel 3:11), not merely for the periodic judgment and purge” of the Atonement but for the “final ‘restitution of all things and the establishment on earth of the eternal Place of Safety - the City and Garden which was from the beginning - the Eighth City whicc is the Pattern-in-the-Mount of all that has life through the Spirit of God.”