If you are certain the kernel picked up the sound card (and the speakers are powered on and connected properly
), you might want to try and check the mixer volume.
The device is usually /dev/mixer, and sometimes the volume can be set too low. You could also try 'play -v 10 <soundfile>' to test playing a sound at a higher volume.
Hope this helps... If not, does "cat /dev/sndstat" do anything for you?