Lol, "You wanna hear God speak? Read the Bible. Oh, you wanna hear him speak out loud? Read the Bible out loud!"
I'm not sure it makes any difference, but I have always thought he spoke out loud to Adam in the Garden, and probably to people for centuries after. One reason to think so is that his dealings with mankind were more plain, back then, and have since developed into now speaking through his word, and by the Spirit of God. Back then, people didn't say, "Jesus is telling me to...whatever" unless God told them directly. The imaginations of their own mind were, in one's own conscience, considered only that. And the false prophets were obvious.
—At least, that is how I see it, and it makes sense to me. It was a different time.
I'm not sure if this passage supports what I just said, or does it, rather, seem to deny it? Hebrews 1:
"1On many past occasions and in many different ways, God spoke to our fathers through the prophets. 2But in these last days He has spoken to us by His Son, whom He appointed heir of all things, and through whom He made the universe.…"