The apostle Paul speaks of “the tongues of men and of angels,” indicating that spirit persons have language and speech. (1Co 13:1) Angels, and Jehovah God himself, have been heard to speak in voice sounds and languages audible to men and understandable by them. But it is not to be supposed that such would be the voice with which they communicate with one another in the heavens, for an atmosphere such as exists around the earth is necessary for propagating the sound waves of voice that is audible and understandable to the human ear.

The instances in which God or angels spoke in a voice in the hearing of men would therefore be a manifestation of their speech as transformed into sound waves, just as appearances of angels to the vision of man required either a materialization or a transmitting to the human mind of a pictorial image. Today even human scientists can convert the sound-wave pattern of an individual’s voice into electric impulses that can be transmitted to a receiver, which can change those impulses back to sounds closely resembling the individual’s voice.

Angelic voices. On other occasions when God ‘spoke,’ angels were used as his representatives to provide the vocal manifestation. Angels represented God in speaking to Moses in Mount Horeb and to Israel, assembled near the foot of the mountain. (Ex 34:4-7; 20:1-17; Ga 3:19) These angels sometimes did not present any visible appearance of a form, as when the voice came from the quaking, smoking mountain. (Ex 20:18, 19; De 4:11, 12; Heb 12:18, 19) At times they made visionary appearances (Da 8:1, 15, 16; Re 14:15-18) and on several occasions materialized in human form to bring spoken messages to men.​—Ge 18:1-3, 20; 19:1; Jos 5:13-15.