aplay -l
lists the audio devices detected, also:
cat /proc/asound/cards
If there's a sound device you want to disable, edit /etc/modprobe.d/alsa-base-blacklist.conf. Mine looks like:
# Comment this entry in order to load snd-pcsp driver blacklist snd-pcsp # Comment this entry in order to load pcspkr driver # HDMI sound on ATI graphics card: blacklist snd_hda_codec_atihdmi blacklist snd_hda_intel
Sound can be restarted without restarting the whole box:
/etc/init.d/alsa-utils restart
It can sometimes help to check alsamixer. Make sure the card isn't muted.