Initially, Super 8 film was a silent medium. At some point there was a sound component, with a magnetic audio strip on the film. This form is rather forgotten. As far as I know, there is no new sound super 8 film made, and no processing available for sound super 8 film.
However, I'm not sure whether that means...
a) Super 8mm sound film is un-processable... perhaps it can be processed, but you'll get a return with no sound strip
b ) Sound Super 8mm cameras can use non-sound film and vise versa.
c) Super 8mm projectors can play sound film and vise versa.
As I said, I don't believe you can get new super 8mm film with a magnetic audio strip, part of the reason, I think, that you'll find seemingly cheap editing stations, sound super 8 cameras, etc. on ebay.