I was just wondering the same thing actually! Would they have had sound or did they just flash an image at you and hope it sticks. Being from the 20s I would guess the latter.

I did film at school, they said something about sound and that, I can't remember though, it was the only subject I failed eek The old 'you will need this information one day' has hit me! lol

Cheers.
Kye.

Thanks for reading!