Just remember in the much larger (and noisier) area of BB, or even Magnolia, sounds like this will generally be more dampened than in your home. So you may think the BB sample has less noise, when in reality, it may not.I haven't actually noticed it when watching movies. The only time I've noticed it is when I'm going through menus on my htpc. When one of the menu screens becomes significantly brighter, I can hear the pitch and volume of the noise go up. I can hear it from 6 ft away if the room is quiet. From directly behind the tv, I can hear some level of noise all the time. It actually sounds like a small pc fan.
I have 14 days to return it so I think on Sunday I'll go down to Best Buy and see if I can notice the same noise on the display model. At this point, I think it's something I could live with but if other models don't exhibit this behavior, I'll probably just exchange it.
edit: I'm 32 so I still have some hearing left.