bug in libsdl can bork Wesnoth sound on ubuntu
see:
https://bugs.launchpad.net/ubuntu/+source/libsdl1.2/+bug/203158
the fix:
sudo aptitude install libsdl1.2debian-pulseaudio
reference:
http://forums.wesnoth.org/viewtopic.php?f=4&t=27653&sid=22cd10cf646d4104cb122c2c10b2c5d8&start=15
and
https://bugs.launchpad.net/ubuntu/+source/wesnoth/+bug/442535