recently, i was messing around with sound settings in ubuntu and somehow managed to make it where sound no longer emitted from the headphone jack. normal speaker sound was still functional however. no matter how much i tried changing settings back, i could not restore the headphone audio.

i followed the steps on: https://wiki.ubuntu.com/Audio/InstallingLinuxAlsaDriverModules

and the problem was resolved.

summarized, to install latest alsa drivers…
sudo add-apt-repository ppa:ubuntu-audio-dev/ppa
sudo apt-get update
sudo apt-get install linux-alsa-driver-modules-$(uname -r)