I’ve recently gone back to test driving the latest versions of Ubuntu as I don’t have the time to keep recompiling Gentoo or playing with the breakages I get in Debian Testing/Unstable mix.
One of the key tools for me is Skype, so during the latest updates to Ubuntu Raring Ringtail it seems to have screwed with the audio. It now crackles and buzzes and not just necessarily on Skype. The fix was published on Skype forums though and it’s caused by timer scheduling being brought in rather than using the old irq method:
Open up “/etc/pulse/default.pa”, find “load-module module-udev-detect” and add to the end “tsched=0”. It should look like:
load-module module-udev-detect tsched=0
Reboot and the crackling should be gone.