How to auto hide launcher when in windows are maximized?

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http://askubuntu.com – I have just installed 12.04 LTS 32-bit. I have been using Ubuntu 11. When I was using Ubuntu 11, I have known that the launcher can be set to auto hide when windows are in full screen mode and appears again when it is in small windows size. But with 12.04, this thing can't happen. Another thing, there is no sound when I log into Ubuntu. The rest are no problem. (HowTos)