The solution is simple: you have to install the corresponding library (libasound2-plugins on Debian, thus probably also on Ubuntu).ALSA lib conf.c:3314:(snd_config_hooks_call) Cannot open shared library libasound_module_conf_pulse.so
Note that you may encounter this problem although you know that this library is installed, which was my case... The point is that the game has ben compiled for 32bit machines, so you need the 32bit library. So in that case, you have to install the 32bit version, that is under Debian/Ubuntu:
and your sound will be backsudo apt-get install libasound2-plugins:i386