The House didn’t actually speak with a voice. Rather, Miranda had made a series of spelled mirrors when she became its Head. They were keyed to her voice and presence, and if the House wanted to say something to her without being addressed first, the words that appeared on the mirror’s surface would be accompanied by a faint chime. No one else in the room would see the words or hear the chime ring. The spell also allowed her to respond mentally, thus enabling a completely secret conversation, if necessary.
I don't know why exactly but this reminds me of the scene in The Office where Dwight is a co-owner of a hotel in hell (but not the manager). It's like this mirror enchantment is half-cool but also very pedestrian. You have to go look at the mirror if it chimes? That sounds kind of incovenient considering there is also silent mental communication ? Like, why not go all the way with it?
