I think just about all power supplies do this, but at different frequencies and different volume levels.
Both my last two laptops have audible power supplies - when they are used you can actually hear a fizzing / buzzing from them. If you increase power usage (e.g. run a game), it raises in volume. But literally, I have to have my ear next to them to hear it, it's so low-level.
And almost all electrical appliances do the same, even without considering things like fridges with moving parts. TV's buzz, hum, chirp, whistle, click, and thrum. So do DVD players even without a disc. So do games consoles. So do mobile phone chargers. It's just a matter of whether you can hear it from your usual usage position or not.
Personally, this is one of the reasons I lock electronics away out of sight. Because I *can* hear those sounds if I listen for them. They are actually my principle point of diagnosis. I can remember phoning up an engineer years ago for a Sparq drive (a sort of Zip drive, but 1Gb and much faster) - we spoke for ten minutes discussing which sounds were different so he could narrow the problem down. You feel a pillock but it's a large part of knowing how a machine works.
And power supplies, I *know*, make buzzing sounds. Some cheap ones even reflect individual disk actions in their sounds (so when your disk is busy, you can have a changed pitch which sounds like a hard disk clicking coming FROM the power supply as it's current changes). You'll know if you use a lot of machines that a lot of cheap laptops actually pick up even mouse-motions from the display on their sound card (I have a model in the room next to me connected to a projector and speaker system that DRIVES ME MAD because as you move the mouse around the screen, you hear a FFffrrrrppp sound on the speakers).
Power supplies buzz. Maybe the buzzing has changed with the firmware update, but they have always buzzed. I'm just amazed that anyone in this day and age has a house quiet enough to hear it without their ear next to it. I have what is possibly THE quietest house I've ever lived in, with double-glazing and zero internal noise, and I do hear my laptop power supply but ONLY when it's by my ear (the plug socket is behind the sofa and the power supply rests on the top of the back of the soda).
I don't doubt it buzzes. I just doubt that it's actually a problem for anyone at all.