Noire's voice will usually be apathic. Since she learned how the human mind works, she'll sometimes use other tones in order to make people feel uncomfortable when questioning her power, when talking to her or when messing up her act when she needs to 'seduce' the target into thinking he's safe.

Usually, she'll have a very monotone, very apathic tone, but she can also use her angry, cynical or loving tones, depends how she wants her target to feel.