Sound preferences is gone
 

A couple of weeks ago, I realized that the "Sound Preferences..." button stop working. When I click on it, nothing happens.

Then I proceeded to search for it on "Administration" and "Prefernces". And then I understood what happened. It simply vanished for some uncanny reason.

So now I need to know if there is a way to reinstall it through apt-get or if not, know what is the source package to build it from the source.

Which release version of Ubuntu are you using? Do you mean the Sound option under System Settings?

10.04. I mean the sound preferences that shows when clicking in the sound icon in the top of screen, which is the same that shows up in the administration or preferences when clicking in System in the top of the screen

It is possible that your user profile has an issue.
I would just create a new user, don't forget to make it an administrator for your sudo to work, then log in with that user.

I had this sort of problem where a certain video streaming website only played for 5 min (all browsers). I could not figure out why so I created a new account. Problem solved.

Unfortunately, it did not work.