I am getting this noise too. It is very annoying. I have tried many things to alleviate the noise, with no success. The noise is ony in the front headphone port. If I connect the same headphones to the rear port, it is clear as a bell. The sound doesn't start until about 5 sec after the win 7 "start windows" screen appears (I am guessing that is when the audio driver loads) and continues until about 4-15 seconds before the machine shuts off. I originally built this amchine and installed the hardware using the standard windows drivers. As a result, I had a driver for the audio that was made by Microsoft.
High Definition Audio Device
Microsoft
7/13/2009
6.1.7600.16385
I replaced that with the latest and greatest driver for the GA-H55_USB3 on the Gigabyte website as of today, 2/26/2011.
Realtek High Definition Audio
Realtek
7/28/2010
6.0.1.16167
It had no effect at all on the noise.
I have moved the cable that suns from the front panel to the socket on the back edge of the motherboard (near the I/O ports). I have unplugged and rep[lugged the cable. When it is plugged in, the noise continues unchanged.
However, I have an additional troubleshhoting advantage most do not have. When I built this machine,. I built 2. One for me, one for a friend. Built at the same time. Identical in ever way right down to software installed and versions. The other machine does NOT have this noise. Mine does. His never did. Mine always did.
I am increasingly convinced this is a motherboard hardware problem. It is VERY annoying. Any ideas about what to try before I go through the hassle of RMAing this board?
Thanks