These days the attack against the the Apostle Paul is stronger than ever (part of the "falling away" that he spoke of). One way people discredit him is with the two recountings--in the Book of Acts--of his conversion experience on the road to Damascus. Acts 9:7 says, "And the men which journeyed with him stood speechless, hearing a voice, but seeing no man." In Acts 22:9 we have: "And they that were with me saw indeed the light, and were afraid; but they heard not the voice of him that spake to me." An apparent contradiction? Not really. In the first verse "voice" means that Saul's (Paul) companions heard the voice of an unseen man but could not discern the words of said man--as the second verse indicates.
We see that Genesis 3:8 says, "And they heard the voice of the LORD God walking in the garden in the cool of the day: and Adam and his wife hid themselves from the presence of the LORD God amongst the trees of the garden." Here "voice" must mean the sound that the LORD God was making as he made his way through the garden. For the next verse (9) tells us, "And the LORD God called unto Adam, and said unto him, Where art thou?" Clearly the Creator did not speak until Genesis 3:9.