Subvocals don't need mouth movements

Ryan closed his eyes for a moment and she heard his voice inside her skull.
"Gimme a mode check. All stations report in ." His mouth didn't
move, but Anna saw the slight motion in the muscles of his throat as he
subvocalized; the communications bead bonded to his mastoid bone
picked up the silent whisper and relayed it wirelessly to the radio node
encrypted to the protection detail's frequency.

Deus Ex: Icarus Effect, Chapter 1 pg. 14