You need to edit the /etc/apt/sources.list file from your terminal using the following commnad
sudo gedit /etc/apt/sources.list
add the following lines save and exit
deb http://ppa.launchpad.net/minichoco-team/ppa/ubuntu jaunty main
deb-src http://ppa.launchpad.net/minichoco-team/ppa/ubuntu jaunty main
sudo apt-key adv
--keyserver keyserver.ubuntu.com 9220067F
Update the source list using the following command
sudo apt-get update
Install the following packages
sudo apt-get install alsa-source module-assistant
Now edit /etc/alsa/alsa-source.conf file
sudo gedit /etc/alsa/alsa-source.conf
On line 11 you should have
Save and exit the file
Now enter the following command in terminal
sudo m-a a-i alsa-source
Reboot and then un-mute headphone & speaker in volume control.You should now have sound from both the speaker and headphone jack.
-- You may need to un-mute the headphone and speaker to hear sounds after each reboot. Click the volume control and un-mute.
-- You may want to mute the PC beep. Click the volume control, click "Preferences" and select the checkbox for PC Beep to make that track visible. Then mute the PC Beep.
Source from here