To have sound in Ubuntu (Counter Strike 2D) you need to symlink openal lib
1
sudo ln /usr/lib/i386-linux-gnu/libopenal.so.1 /usr/lib/i386-linux-gnu/libopenal.so
And in CS2D Options set "OpenAL Default"
Now you should have sound in CS2D
Fervi
PS. Works with 64-bit Linux, maybe you need change to work in 32-bit Linux