MY WD Passport 1TB

I recently bought the WD Passport 1TB Hard drive and connected it up to my new Tecgnika 24E21B tv using the usb cable, But when i click in to watch a movie on it the movie plays but there is no sound… anyone know what could be wrong? The sound works when i watch ordinary tv. 

If you connect the drive to a computer and play the file on there do you get sound?

Is it just one movie file without sound, or several? What format are they in?