How to stop Ubuntu from talking to me?

Pressing AltSuperS will disable or enable speech dispatcher.

The last thing you should hear is "screen reader off" :-

ps. The Super key is the "windows" key...

Go to the Settings application. Select Universal Access. You will see a tab labeled "Seeing". In there should be Screen Reader. Turn that off.

I had the same problem maybe, starting with Ubuntu 15.04. The Screen reader is off, same with the dispatcher setting; but it keeps telling me what I'm typing.

I have running four dispatcher, all at the time that can't be killed because they're starting again directly. To solve my problem, I went to System Settings -> Sound. On Applications, I muted the four speech-dispatcher.