Jack

Remove pulseaudio

Pulseaudio, like Jack is a sound server, and the two don't co-exist very well, so we might want to remove it

from: http://crunchbang.org/forums/viewtopic.php?id=23930

sudo killall pulseaudio
sudo apt-get purge pulseaudio pulseaudio-utils gstreamer0.10-pulseaudio libpulse-browse0 paman pavumeter pavucontrol
sudo mv /etc/asound.conf /etc/asound.conf-bak
rm ~/.pulse-cookie
rm -r ~/.pulse

Reboot, and install all the required alsa tools

sudo apt-get install alsa-base alsa-tools alsa-tools-gui alsa-utils alsa-oss alsamixergui libalsaplayer0

Test Alsa

mplayer someaudiofile.mp3

While the file is playing, and specially if you aren't hearing any sound, open the alsamixer

alsamixer

check if the output volume (Master, PCM) is up and if the channels are not muted (MM in the bottom. If sound select the channel and unmute w/ 'm' key)