I also am beginning to think the electric power steering is a major contributor to the noise.

Not my car but behold all the glory of a scion etc running. Lol

http://youtu.be/WSNKaVkuuPc

 

anything that puts a load on the alternator/electric system will let it whistle more.
The worst is when the battery is almost dead and the alternator is trying to recharge it, or a demanding audio system is installed incorrectly causing a bad ground and the speakers whistle with the same noise as the alternator.
pitch will change with throttle input.

 

Alternator no doubt. Just turn the radio up, or spend a ton getting a new one installed.