No Sound on Ubuntu 12.04

After I installed Ubuntu 12.04, there are no sound at all on my headphone (rear jack panel).

On Sound settings > playback, it seemed that the sounds were detected after I choose 'play sound'.

Anybody can fix this issue??

Thanks.

https://help.ubuntu.com/community/SoundTroubleshootingProcedure

I just did Step 1 and then reboot my laptop and the sound works.

If you are using Ubuntu 12.04 or later, then execute this command and reboot:

Carefully read and understand what these commands do. For instance, the sudo apt-get install command includes the entire Ubuntu desktop. This will likely create problems for users of the other flavors of Ubuntu -- a Kubuntu user would not want the Unity interface installed. While the outcome of running the suggested command string below may indeed fix certain sound problems, be aware that it is a very blunt approach and could result in unintended consequences.

sudo add-apt-repository ppa:ubuntu-audio-dev/ppa;              \ 
sudo apt-get update;                                           \ 
sudo apt-get dist-upgrade;                                     \ 
sudo apt-get install linux-sound-base alsa-base alsa-utils gdm \           
     ubuntu-desktop  linux-image-`uname -r` libasound2;        \
sudo apt-get -y --reinstall install linux-sound-base alsa-base \ 
     alsa-utils gdm ubuntu-desktop  linux-image-`uname -r`     \     
     libasound2;                                               \ 
killall pulseaudio;                                            \  
rm -r ~/.pulse*;                                               \
sudo                                                           \ 
    usermod -aG $(                                             \
          cat /etc/group |                                     \
          grep -e '^pulse:' -e '^audio:' -e '^pulse-access:'   \
          -e '^pulse-rt:' -e '^video:' |                       \
          awk -F: '{print $1}' |                               \ 
          tr '\n' ',' |                                        \
          sed 's:,$::g'                                        \ 
    ) $(whoami)

Paste the whole code block into your terminal with CTRL-SHIFT-V, then press enter.

Try this:

sudo killall pulseaudio
sudo alsa force-reload