I rarely go log into IRC channels, and had not done it after I got this laptop last summer. When I do (there will be an unbutuforums meeting I can attend in a few minutes), I use xchat. I know there is a whole set of IRC clients, but this is the first one I used, and it fits my very basic needs.
Surprisingly, there was no sound on this default fresh install (Ubuntu Hardy). I created a
~/.xchat2/sounds file which was missing and copied a .wav file from
/usr/share/sounds, then enabled it from xchat preferences menu. All set!
Looking around, I found a xchat-gnome package that I will try soon.