The closest you can get to "training" is to use the little volume-calibration assistant in Speech Preferences. Go to the Speech Recognition tab, and the Listening tab below that, and click the "Volume..." button in the lower right: you'll get a dialog with an audio-input meter, a dialog, a few phrases to speak, and instructions on how to calibrate your setup.
gorickey: read that tiger page again... that's all about screen-reader features, not speech recognition.