Mouth slit
From Tardis Wiki, the free Doctor Who reference
What ArcHivist Hegelia termed the mouth slit was the equivalent of the humanoid mouth seen on the faceplates of certain subspecies of Cybermen. (AUDIO: The Early Cybermen)
The Cybermen produced by Cybus Industries in Pete's World had mouth slits which gave off blue light whenever they spoke. (TV: Rise of the Cybermen et al.) Similar Cybermen appeared in N-Space, associated with the Cyber Legions. (GAME: Blood of the Cybermen, TV: A Good Man Goes to War et al.) Later Cybermen, associated with the Cyberiad, also retained this feature. (TV: Nightmare in Silver et al.)
