Comment 13 for bug 574137

Hello Jim, I have exactly the same problem although just lowering and increasing the volume or switching from one application to another (say Skype to rythmbox) will suffice to start the scratching audio. Another thing I notice, When audio is poor if I go to

 System -> Sound -> Hardware
and set the Settings for the selected device:
Profile: to off
then put it back to Analog Stereo Duplex

The quality temporarily comes back to good/excellent.

I do know if this helps in anyway (that is my first ever contribution to the Linux community).

Cheers