Comment 15 for bug 770555

... and finally microphone in Ubuntu 11.04 Unity 2D workes after removing pulseaudio (because of it no volume control on panel). Still have interrupts in line 16 but much lower. So, I guess problem was in pulseaudio. I do not know if pulseaudio can be fixed, but removing it worked for me. (hope it will work more than a day :-)