Get ready for mind blown! Mine does the stutter chatter thing too!!!!!! It must be the video card. And here's another strange tale. My large screen tv does it too, similarly, like it catches the sound of a vowel being spoken and some poor child with a stuttter ... holds it for a few seconds and goes on. But there is not relation between the HP Ain1 and the TV. TV is on Comcast and PC is on Verizon.
I think you hit it right on when you said the plastic case warming up. I had forgotten that I had deduced that myself a few months back. My pc sits just aboumt even with the window and it's aboumt 12 inches away. It was probably cold in the mornings, like myself, coffee klatched in hand and then boot it and I'd hear the sound. Then ear and nose, eye to the origin of the sound and one day I finally dismissed it as the case warming. Good call. I had forgotten that.
The chatter we both have must be something wrong with the video card and or audio or we need some sort of a fix or new driver. I have been asked to update the driver about a half dozen times since January and I have. But nothing seems to fix that chattering stuttering ocassionaly. Not enough to bother me terribly really.
I also love the compactness. For years I said I'd never get another desktop. I purchased a Toshiba Laptop in 2003 and another 2005. The older one finally died about 2 years ago. I had the 2005 left and I bought a netbook and a Xoom tablet. This desktop is the only desktop I've purchased since the 90's and I dig it. I opted for no touch screen, I see how messsy my tablet screen is all the time. And because it was the large 23", plenty of real estate on the screen, I opted not to have the 2nd monitor capability, which I used on every laptop. So less those options I think I paid $699 or $799. Probably the latter.
G'day! Keep in touch here and we can compare issues. Let's hope for no more. Jack ":-D