Smaug, Smauog or Smog?

How does one pronounce the name of the most terrifying dragon in all of Middle Earth?  “Smauog” is enunciated by the characters in Peter Jackson’s Hobbit films.  Is that Tolkien-approved correct or a writer-director’s whim?  The intrepid fans at The Land of Shadow went on their own quest for an answer, and what they discovered can be learned here.