sorry for my poor english :p
I recently purchased a Thinkpad T430 series laptop and dual booting(Ubuntu 12.04 and Win7).
whenever I shutdown Ubuntu, I get a "pop noise" for about a second right before the machine actually powers off .
I've tried a lot of linux os , and the same problem, pop noise on shutdown. (For example ubuntu 12.04/12.10/13.04, Fedora 17/18, centos 6, opensuse...)
I doubt it's caused by alsa-driver, the drivers did not poweroff sound card before system shutdown.
My sound card is "Realtek alc269" (detected by Everest on Windows), but in ubuntu, "aplay -l", it tell sound card is "alc3202"
I got some information from http://www.alsa-project.org/main/index.php/Detailed_HDA_changes_v1.0.24_v1.0.25#HDA_Intel_driver It looks like driver should turn "EAPD" off before shutdown.
Any suggestions would be appreciated. Thank you.