If you use Ubuntu Karmic Koala beta and have a Intel sound card, you must be hearing a popping sound every now and then. This is a known bug and here is a temporarily solution for it.
Press Alt + F2 and type:
gksu gedit /etc/modprobe.d/alsa-base.conf
And comment (add a “#” in front of it) the last line called “options snd-hda-intel power_save=10”. Basically, this is how the line should look after editing it:
#options snd-hda-intel power_save=10
Then save the file.