When the key is in the ignition and the car is about to be started, there is a loud, high pitched noise, like the sound of a humming, constant beeping sound...not really heard by much people if you ask, but when you listen further it comes from the rare back wheel...sound the loudest there...any help??

If you mean when you put it in accessory mode, and there is a methodical humming sound coming from the rear, it is your electric fuel pump building pressure.

Totally normal, Subaru has a tendancy to have one of the loudest fuel pumps out there. On my Sti you can hear the fuel pump prime outside the car and about 10 feet away.

my subaru had an electric antenna that would hum every time l turned on the car..