Description: After upgrading to [linux] 3.9.2-1 from [linux] 3.8.11-1 an audio flicker began to occur every few seconds. It acts as if headphones were being rapidly plugged in and removed, resulting in the sound skipping every few seconds, no matter the application playing the audio. Evidence of these "imaginary headphones" comes up in a few ways, using GNOME, the top bar has a volume button, which expands to include a headphone logo, which constantly flickers in time with the audio flicker. Also, in the sound menu, a headphone output appears in time with the audio flicker.

Additional info:
* package version(s)
Was upgraded from [linux] 3.8.11-1 to [linux] 3.9.2-1. Operates fine in 3.8.11-1, but audio flicker occurs in 3.9.2-1.

* config and/or log files etc.
Relevant hardware listed here:
$ cat /proc/asound/cards
0 [SB ]: HDA-Intel - HDA ATI SB
HDA ATI SB at 0xfe500000 irq 16
1 [NVidia ]: HDA-Intel - HDA NVidia
HDA NVidia at 0xfe080000 irq 25

$ lspci | grep Audio
00:14.2 Audio device: Advanced Micro Devices [AMD] nee ATI SBx00 Azalia (Intel HDA) (rev 40)
01:00.1 Audio device: NVIDIA Corporation GF116 High Definition Audio Controller (rev a1)

Steps to reproduce: On what appears to be most Intel HDA hardware, simply upgrade to [linux] 3.9.2-1 and observe (at least for me) in GNOME the system sounds interface to see headphones flickering.

Steps for temporary workaround: Downgrade [linux] package to previous version, in this case 3.8.11-1.

Others have reported the same or similar bug, forum post is here:
https://bbs.archlinux.org/viewtopic.php?id=163208