The other week we could not trace the whine/buzz anywhere. We went ALL over the house, listened to every device, stood outside - nothing. THEN .... traced it to the electric door bell box just above the inside Hall door. A delivery man had rung the bell an hour or so previously and the bell push had stuck in. As soon as it was released the noise stopped.
What colour shoes/boots to wear.
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. For the next three months or so there was a high-pitched whine that only I could hear, and only when it was quiet. It went after a few months.....or I just got used to it.