Volume no longer works on Mac Air

[GIZBUG]

I have my volume turned off, MUTE is off, but I hear no sound, not even when I press the volume up/down button. Any idea how to fix this? Not sure if I accidentally pressed a button/button combo to turn it off, but I hear nothing. Help.

 

[chabig]

Check System Preferences > Sound > Output and make sure your Internal Speakers are selected.