HD audio buzzzzzzz
So… I’m using a dangerously long audio cable to connect my computer. It’s always caused a buzzing sound when connected to the amp but not my computer. No surprise there.
After a recent hardware refresh, though, it started buzzing while the computer is powered up and connected. It will start buzzing about 10 seconds after a sound is played and continue buzzing until another sound is played. This behavior immediately made me think of a Karmic release note about putting sound cards to sleep.
After figuring out where the kernel documentation is for Ubuntu (it’s the linux-doc package), powersave.txt confirmed my suspicions. The easiest solution for me was to disable this sleep behavior. I’m using a desktop and while it might be nice to put my sound card to sleep, it’s really not necessary.
It turns out that this option is explicitly set to the default in Ubuntu 9.10 in /etc/modprobe.d/alsa-base.conf. To disable this behavior, all you have to do is set power_save=0 in the snd-hda-intel options line. You can change the setting in the running kernel via /sys/module/snd_hda_intel/parameters/power_save.
After a quick “echo 0 >> /sys/module/snd_hda_intel/parameters/power_save”, everything was back to normal, and I could get on with my day.