FILMED WITHOUT SOUND?

The first time I put in my Conformist DVD it asked me what language I wanted to watch the film in (English / Spanish / Italian / French / Portuguese). I always like to watch films in their original language, so I selected "Italian". Once the film started, I noticed that the voices didn't quite match up with the actors mouths. Ok, I thought, perhaps it is like Antonioni's The Passenger and, although it is an Italian film, it is in English. I tried the English language track and that didn't seem to quite match up either.

Now, I know that sometimes movies are filmed without sound and the voices are added afterwards. Is that the case with this film? I am assuming it was originally filmed in Italian. The only thing that makes me think for a split second that it was filmed in English is that the clips that they show in the extra documentary featurettes are all in English.