Best way to study this is to write the English "huh" into Google translate and observe how this "expression of scorn, anger, disbelief, surprise, or amusement" is vocalized in different languages. Comparing various written forms is just stoopid. You can clearly see it is the same wide-mouthed grin which produces same wide back-vowel [ɛ] or "ä". "H" is just the associated btreath-sound.