I installed ubuntu 13.04 but I don’t have hdmi sound output option. I followed these steps(http://askubuntu.com/questions/296445/no-sound-on-tv-with-hdmi-ubuntu-13-04) and it solved my problem:

That is what is called a ppa. It is just a place you can add to apt so it gets updated also. What you need to do is add the ppa to your system and update it… Here is what I did when 13.04 came out and it worked for my HDMI sound issue.

sudo add-apt-repository ppa:ubuntu-audio-dev/ppa
sudo apt-get update
sudo apt-get dist-upgrade