Greetings in that Divine and Most Precious Name of Our Lord and Savior Jesus Christ!
When God speaks to people like Noah, Abraham, and various other people in the OT...how exactly is God communicating with them? Is it truly in speech?
This is the kind of question that comes up in Christological discussions. According to our Orthodox theology, only Jesus Christ the Incarnate Word is a human being with human attributes including the capabilities of human speech. God the Father is does not have a voice, as God the Father is Immaterial, Infinite, Immortal and altogether of a different, Divine substance which is not part of our physical realm where speech occurs. So from this perspective, the "voice" of God must have been something more akin to a perceived sound in the ear of the mind, from the heart, like the voice in the cave heard by Elijah. After the coming of Christ in the physical form, God can speak to us in a vocal form, but I would think its safe to assume that any reference to the voice of the Father or God speaking is purely symbolic, and that it is more likely an explanation of a kind of vision. Even when God the Father spoke at Jesus baptism or at the Mount, we should assume that the people did not hear some loud, thunderous and physical voice from the clouds, rather that all those who heard shared the same momentary vision of God's speaking.