Thanks for your response Brian.
there is no specific Super 16mm stock; it's all the same 16mm stock. Which means it's a matter of the format the camera allows to be recorded - the size of the gate? Does this mean that the area used for audio in regular 16mm is just film emulsion but used in a different way to record audio?
Yes, the camera determines what is put on the negative. Ultra and Super 16 formats both assume that the negative will be used as a video or computer source and not be printed to be shown on a projector.
The film stock is made originally on rolls from 40 to 60 inches wide, and cut down for use, so the entire surface is same (other then the factory edge printing.
16mm Sound prints generally require the sound track negative to be recorded separately, and the sound is printed from the sound negative on the sound track area. The picture negative is masked in the printer so it leaves the soundtrack area free of information.
Can double perf stock be used in regular 16mm cameras?
yes. Some older cameras REQUIRE double perf stock unless modified. Most cameras will just ignore the extra holes, and as stated above the second row area will not be printed if making a conventional print, with that area reserved for the sound track negative.
Until super 16 came out, the default format for camera stock, was often double perf. Kodak saw that super 16 would be a good format for digital origination, and so changed the default to single perf, making double perf stock a special order in many cases.
Unless you are using a camera that demands double perf, or one of the high speed cameras that also has special perf requirements, you can shoot regular 16 with either stock. Even mixing the two and still get it printed or transferred as one final roll.
I don't know where the concept of Super16 film came from, other than perhaps folks having to order single perf when double perf was the norm.