Mac Pro :: Does Your 2008 MP Give A Slight Electrical Humming Noise?

..by the power unit at the back of the machine - where the power cord goes in.

I happened to be switching out displays at the back of my MP today. Could hear the fan at the lower back portion of the machine (as normal). but this time could also hear a very slight electrical hum just by the power unit -- is this normal (the hum) does yours have this hum?

I never heard it before. guess my head was never that close to it when the MP was on the floor. but since i moved it to the top of the desk my head is closer to it when I switch out the DVI ports

Trying not to be obsessive. I'll run before the white coats turn up by the front door