OP, it looks as though the iPad has a mute switch above the volume control, just like the iPhone. If I were to guess I would say it has a vibrate feature.
http://images.apple.com/ipad/home/images/hero4_20100127.png
how do you know that is a mute switch?? couldn't it be a master on/off switch, or for some other function? what makes u assume it must be a mute switch?