[ Sebastian who? Sebastian patience is gone. This is Sherlock, plain and simple and grouchy, speaking very calmly and matter-of-factually. ]
Basic scare tactics. Obvious. It's not as if it's difficult to alter audio like that. Simple distortion. The person outside: Unidentifiable. They've more than enough people - drones, I suppose you'd prefer - to spare around the town to assign one to each house.
Indisputably, something larger is being alluded to, but without more evidence, it's really useless to theorize, and you're merely giving anyone in larger authority the reaction they'd like to see.
So the phone can stop ringing in excess now, if you'd please.
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