When mousing over each character in character selection, a sound effect plays that matches the animation.
When mousing over the sentinel, there is a metal scraping sound and his mouth opens slightly while adjusting, creating a disjoint between the sound effect and character animation. It seems as if the animation sound is coming from the character. The over-saturated lighting (present everywhere in LE - but even worse in this case) causes the teeth/inner mouth to look strange, adding the effect.