Ghost voice in the beta is very computerised, I thought it was brilliant in the Alpha. For my point of view, today's computers can speak very clearly and human like (i.e. IOS's Siri, and other speech assistant services). In the Alpha, Ghost's voice felt more personal, and that it was taking to the player,
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I wasn't there for the Alpha so I have no real comparison, but Ghost is a small, floating drone-type-thing. It has no lungs nor does it breathe air. A wizened, human voice would just sound odd for what the source was.