IOS – How to activate voice dictation on ipad 3

I found the answer from iMore's How to turn on and use Siri-like Dictation on your new iPad:

If Dictation gets confused about any of the words you speak, it will underline them in blue on the screen. If the word is incorrect, tap it to get a popup menu with alternatives. Tap an alternative to switch to it. You can also simply edit voice dictation text like any other text.

Sure enough, single-tapping on Claire gives me an option to change the text to Clare, and of course it works other ambiguous words.

A particularly useful example is when you mean Buy, and the dictation types By, with a blue underline. Tapping on that gives the two alternatives Buy and Bye.

As of iOS 5.1, Voice Dictation is not capable of being started from external keyboards.

There is a workaround. The solution is that when you want to dictate, press the ⏏ key (eject) on your external keyboard. This should bring up the virtual keyboard on the screen, from which you can then start dictation.

Note: This key doesn't work like other function keys until you have tapped into a text entry field and have the flashing cursor.