Sound in the 16mm world exists in two ways, optical or mag stripe, on the film itself, and as a synced external tape, usually recorded in 1/4 inch, but you can crystal-sync other formats. The camera puts an optical marker on the film, and an audio marker on the tape, to time code.
The most practical camera for creating sound directly on film is the long discontinued Canon Scopic (6mm film is sold with and without a magnetic stripe). Normally however you take your original film and audio tape and have a work print made, with a mag track, and you put your originals away for later. You then edit using your work prints with an audio track.
When finished you take your original print and have it "conformed" to the work print. Remember film is not digital, each time you make a print you are a generation away from the original. The final product usually uses an optical track, not a magnetic stripe.
As an alternative you can take your film and make a work video, and edit that, and again conform the original.
Or as a second alternative you can make video from the original film and audio, and that becomes your final product.
If this all sounds tedious and complicated, that is because it is. Before the advent of digital video, even video was treated this way, you made copies, edited them, producing and EDL (edit decision list) and then went back and conformed the original. With analog video, like film, each copy was lower quality than the original.
Digital video has ended this worry about the original, since each copy is exactly the same as the original.
In the real world of analog film when you went to the theater you were [are] seeing the forth generation. Original>>mastercut>>master-prints>>distribution prints.
16mm film is sold with and without a magnetic stripe, double or single perforation. You can shoot standard and super 16.
