Humming noise in dashboard?

Has anyone heard a humming noise from the dashboard/radio area? (At least that's where it sounds like it's coming from.) The noise is similar to the high-pitched tone you hear when you've left your headlights on and you turn off the car - Just not as loud. I wasn't using the radio/AC or Heat. It stayed on until I shut off the car and restarted it. ??? I hope this won't be a continuing problem.
 
The best thing to do is put the radio very loud and you won't hear it anymore. I did this for every problem i had in my 1991 accord and it worked perfect, in my head i thought the noise was gone.
 
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