And when for when, A.V.; behold for behold it, A.V.; there came a voice of the Lord for the voice of the Lord came unto him, A.V. There came a voice. The A.V. is surely right. The Lord has only one voice; and φωνὴ κυρίου is that voice.
The grammatical effect of κυρίου upon φωνὴ is to make it definite, as in ἄγγελος κυρίου (see Acts 5:19, note).