They shouldn't lose just audio in time - you can end up with parts of the reels that become too brittle to feed through a projector/reader. It's part of why I think preservation of these reels should be happening now, while it still can be done.

As far as some having no audio, that can actually be the case. I don’t think that's normal on 16mm, but some 8mm definitely is missing audio tracks. Depending on the camera used, they may have also not cared about audio for a football team, for instance, on plays. Because film cameras are so noisy as they run, it’s normal to use a separate reel-to-reel recorder for audio as a separate audio gaffer's job in the film industry back then. (That still continues in the modern form most of the time now) It's possible at the time they did that with those contests and you have another reel to reel recording somewhere? I've never seen those for anything than concert recordings in our piles.

I would look at the film when you get it back and hold it to the light. You can definitely see the waveform on film reels if it has it. I know we definitely have some from the 50s that didn't have audio. When I presented it to the community I added a recording of our modern band playing one of their concert marches.