There are two accounts of the wilderness meeting. The other one disagrees with the one you just cited, in which no one heard any voice. The account was not given by a direct witness, and according to the unknown author, who is often assumed to be Luke, the account would have been provided by Paul, who was supposedly an associate of Paul. There were no witnesses to what was said, and apparently, according to Paul, through the author of Acts, no one saw anyone. According to Yeshua, self-witnessing, "is not true", and you should not believe anyone who says, "He is in the wilderness".
New King James Version 22:9
“And those who were with me indeed saw the light and were afraid, but they did not hear the voice of Him who spoke to me.