This problem looks to me more on the software side.

After booting the sound randomly disappears after some time. earlier I used to get the message "KDE has detected that the following devices have been removed."

After updating to Raring, I no longer get this message, the sound just gets turned off.
After a reboot, sound works fine and randomly after some time shuts off.

Whenever I play some audio, I can hear some sound tryung to load but it does not (it's like the static noise that comes when the sound starts).

It looks like some conflicting software settings.

Also noticed that when I keep a video continuosly playing this does not happen. It happens when I pause a video for some time and then play.