That's handy info...
OK, this seems to be related to a known bug in either gstreamer, or pulseaudio... see here:
First, make SURE Synatic, Ubuntu Software Centre, and Update manager are ALL CLOSED.
Lets try adding the PPA mentioned and then updating those packages....
First let's install the ppa-purge package, so we can back out of the changes easily if necessary:
If the above command fails with ANY errors, STOP NOW, and let me know... DO NOT carry on with the following instructions yet.
sudo apt-get install ppa-purge
OK, now let's add the PPA:
sudo add-apt-repository ppa:diwic/fighting-rewinds
then update the package cache and upgrade the system
sudo apt-get update && sudo apt-get upgrade
Now reboot, and check your audio.