Power adapters and noise canceling headphones

I made a recent discovery concerning noise canceling headphones and laptop power adapters (US models, anyway). If the power adapter isn't grounded, when the noise canceling feature on headphones is turned on, the combination is static feedback...and plenty of it. I have several computers, 2 HP desktop (grounded) 1 HP Pavilion Laptop (grounded), 1 Dell Inspirion 600m (grounded), a Toshiba Satellite (not grounded) and my newest addition, my Acer Aspire One and it's power adapter is not grounded. On any one of them with a grounded power supply, laptop or desktop, I can plug the headphones into the headphone jack, turn on the noise canceling and nice quietness is mine. On both the Toshiba and the Acer, plug in the headphones; turn on the noise canceling and hhhmmmmmmmm. Disconnect the power adapter from its jack and it works as it should, nice and quiet. If you touch the steel around the VGA port on the laptop (and you are grounded), again, nice and quiet. No question, a lack of grounding issue with the power adapter. So today after noticing a HP power adapter's connector tip from an old, donated laptop at work, (I work in technology), and after reading the output specs, I gave it a try when I got home. You guessed it, grounded HP power supply plugged in the Acer charging jack, plug in and turned on the headphones and no hum. SWEET!
I called Acer support about this issue over 10 days ago. The level one support sent out a replacement power supply after repeatedly being told it had to be a grounded, 3 pronged plug power supply and I was assured repeatedly it was. It wasn't. Same adapter I already had. Called back and was escalated to level 2 where I was told that the only power supply Acer makes for the Aspire One is the one that is shipped with it. No other solutions were offered. That's a shame. Funny, I also contacted Toshiba (they don't have a grounded power adapter either) and the first trouble shooting step they have you do for this type of problem is to disconnect the power adapter, remove the battery and press and hold the power button for 10 seconds to "discharge any stray voltage". Isn't that one of the things that a ground is for??? I just ordered a grounded 3rd party power adapter for my Toshiba from eBay.

Any suggestions who or what department at Acer might want to know this kind of info and if so, their contact info? The tech support reps I spoke to, both level 1 and 2, were clueless about grounding anything.
Thanks.