Subaru high pitch whine

This sounds distinctly like alternator whine. Perhaps a audio signal wire is too close to a power cable. Or this may be caused by a ground loop. Improper install of aftermarket stereo/speakers/amplifier?

Disconnect the speaker harness from the radio. Start the car and verify the whine is gone. Check that no speakers are shorted to the chassis, if so, there is a ground loop.

Then try unplugging individual inputs and accessories.

And lastly the radio antenna.

I shall try this, I have the same problem…

2006 Legacy 2.5i