Google knows plenty about you, and for a while there it was particularly interested in your pronunciation of words. If you opted into Personal Voice Recognition almost four years ago, Google would use those words to build "a speech model specifically for you," according to the official blogpost on the matter. You could then access this data from your Google account dashboard.
According to DroidLife, the feature was actually laid to rest some time ago—no one really noticed it. The new Google Search update for Android officially retired the feature, possibly because a new voice recognition engine has been implemented. On its support page, Google said that your old voice recognition data has been removed from the Google Account dashboard and is no longer associated with your Google account.