We have a high pitched whine in our great room, have turned the power to the house completely off including removed the hydro meter and it had no effect on the whine. It really sounds like it should be some sort of electrical issue like the speakers for the home theater or stereo or TV or something similar but as I said we turned the power off completely and it had no effect on the noise.

The noise is only in the great room not in any other part of the house and not in the basement where the hot water heater and furnace are located. It has not been windy so it doesn't appear to be related to vents etc. and I have been up on the roof and there are no external sounds. We also had a TV dish on the side of the house but I removed that and all the wiring and this had no effect on the sound.

I'm out of ideas, any suggestions?

Vacuum breaker on hose bib? Make sure all hose bibs are turned off.