EDIT: I still have this problem as of 6/20/2016 My microphone works just fine in Windows 10. When I try to use Google Hangouts in Ubuntu I am almost completely inaudible over the random noise from my mic. Google Hangouts automatically changes my microphone settings, so muting the broken channel only fixes things for a few seconds. I want to disable the broken channel so that Google Hangouts can't use it.
This is a recording of me making snap noises. The bottom channel is the broken channel which is full of maximum volume random noise. The top channel sounds like the mic does in Windows 10.

I am on a Gigabyte P25X V2 using the built-in microphone.
uname -a:
Linux Hyperion-K 3.16.0-60-generic #80~14.04.1-Ubuntu SMP Wed Jan 20 13:37:48 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
cat /etc/issue
Ubuntu 14.04.3 LTS \n \l
some of lspci output:
00:03.0 Audio device: Intel Corporation Xeon E3-1200 v3/4th Gen Core Processor HD Audio Controller (rev 06)
00:1b.0 Audio device: Intel Corporation 8 Series/C220 Series Chipset High Definition Audio Controller (rev 05)
according to alsamixer:
Card: HDA Intel PCH
Chip: Realtek ALC282