Furnace makes an electrical noise/hum even though the thermostat is set to OFF. Normal?

First time home owner here. The house has an American Standard Freedom 80 natural gas forced air furnace, I believe the unit is a 2016. I noticed lately, since I've turned the thermostat to the OFF position for the warmer months, that the furnace is always making an electrical humming sound. Its pretty noticeable when I'm down in the basement. I was wondering what this sound is, and if it's normal. It's not obnoxious, but it's kind of on the loud side for something that I would think is just sitting off or idle... I also wonder if whatever is making this noise is using a bunch of electricity unnecessarily.
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There should be a switch at the furnace that turns the furnace off. The electrical humming sound is the transformer.
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On 6/7/2018 7:34 PM, catalpa wrote:

Or could it be a fan that should not be running?
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