Google's voice based search Impressive

It is impressive that Google is able to obtain high accuracy for frequently used search terms in voice based search. This is an excellent engineering work. This is not an easy task since the speech recognizer needs to be stable under various accents. It must have required a lot of training data. I believe that they probably used a large scale finite state transducer to map to the correct word. It will be interesting to know what are the main tricks they employed in order to get this high accuracy.