In Episode 12 of the Vampire Knight anime series, Zero encounters Shizuku Hio, the woman who turned him into a vampire. Even before she tries to compel him, he is shown as experiencing a strong physical reaction to her voice. It is clear that he already knew that she was there, so he shouldn't have been surprised to hear her.
Why does he have that reaction? Does her voice have a compulsion before she tries to actively compel him? Is it due to some sort of bond he has with her? Or is there another reason?