The Voice Interface uses Google’s Cloud Speech API, which requires registration.
If you followed along with the MagPi when you assembled your AIY Project, then you will already have a Google account and a credentials.json file. If not then you need to follow the instructions to register and obtain this file.
You may also want to modify entries in the preferred_phrases list on line 111 of speech_reco.py. These provide hints to the google speech recognition engine. I’m not convinced they make much difference, but for difficult to understand words they may improve reliability.
To generate a Snowboy .pmdl file containing the pattern for your watchword, pop along to the snowboy site, register for a free account and follow the instructions to record or download a file. I chose to use the most common watchword on the snowboy site, Alexa, as it had the most samples and would theoretically be the most reliable watchword. You should experiment with whatever word you choose.
So, on to system testing…