Comment 126 for bug 301755

linux-image-2.6.28.15.20 and pulseaudio-1:0.9.14-0ubuntu20.2 here, with the crackling audio (on a Thinkpad T61p).

The fix that seemed to work for me -- and in fact the only one needed at all -- was Jonathan's suggestion of adding the position_fix=1 option to snd_hda_intel.