I know you know this, so this is general information for people unfamiliar with film cameras.
Most 16mm film cameras at the time did not record sound. (I don’t think there are any modern 16mm cameras that do.) Broadly speaking, there are two types of film cameras: ‘silent’, and ‘MOS’. Most people might assume that a ‘silent’ camera isn’t used when recording sound. Actually ‘silent’ means that the camera itself is very quiet, which it needs to be so that its noise is not picked up on the microphone. ‘MOS’ means ‘motor only shot’, though I prefer the other story about the German director who would say ‘Mit Out Sprechen!’. You know what they say: ‘If the legend sounds better than the truth, print the legend.’ An MOS shot is one in which audio is not recorded. MOS cameras, since they are not intended for use with sound, are noisy.
When recording sound there are two ‘systems’. Single-system sound records sound directly on the film, either by exposing the sound track to light (Movietone system) or by recording a magnetic track. Double-system sound records the image on film as usual, and the audio is recorded on a separate tape recorder such as a Nagra. A sound-capable double-system camera either generates a synch tone or pulse and is joined to the audio recorder by a synch cord, or both the camera and the recorder have synchronous motors so that they don’t need to be physically connected. The famous slate with clap-boards is used to provide a synch point. When the sticks come together they are recorded on the film, and the sound is recorded onto the tape. The tape is resolved onto 16mm film (or 35mm film, or super-8 film, depending on what you’re shooting) that is covered in iron oxide (this is called ‘fullcoat’) so that there is a frame-for-frame correspondence between the image and the sound. The image and sound of the ‘clap’ are aligned in a synchroniser (gangs of two or more sprockets) to keep the image and sound together.
Super-8 cameras, which most consumers were familiar with at the time, were originally silent – not ‘silent’. That is, they did not record sound. (BTW: 8mm and super-8 differ in that while they both use 8mm film, super-8 has smaller sprockets to make room for a larger image.) In 1973 super-8 film and cameras gained single-system sound. A magnetic stripe was added to the edge of the film, and the sound was recorded onto it. The sound was displaced three inches from the image. There were also double-system super-8 cameras.
Single-systems had advantages and disadvantages. Since the sound and image were together, they didn’t have to be synched. This was good for ‘home movies’ and for newsgathering, but made editing somewhat problematic. You could either edit for image and lose a second of audio, or edit for sound and have an extra second of image that you don’t want. Or you could copy the film onto fullcoat and edit as double-system.
Auricon made single-system cameras, and I think Cinema Products made some too. I think the Bolex 16 Pro had single-system, but I’d have to look that up. These cameras were used in newsgathering because the film with audio could be processed and aired quickly, without having to synch the image and audio – much like video. But much footage was shot on MOS cameras such as the Arriflex 16St or 16M. These cameras sound a bit like a blender, but since sound was not recorded it didn’t matter. If you look at old footage of events with a lot of reporters, you’ll often see someone holding an Arri 16 above the heads of the crowd or mounted on a tripod. The Beaulieu R16 was often used for documentary work. The R16 was not particularly quiet, but was quiet enough so that it could be used with an audio recorder in noisier areas. This was a double-system camera that used a Pilotone generator and cable to join it to the tape recorder. It was lighter than an Arri, and could accept 200-foot external magazines. (The usual external load in other cameras is 400 feet – about 11 minutes.) A battery was contained in the hand grip, and the Automatic model had auto-exposure. This last feature made it useful in situations where a shot had to be made quickly, such as in a war zone. (I’ve seen several R16s in footage taken during the Vietnam war.)
So in a nutshell: Audio was generally not recorded onto the film, though single-system cameras could do it. Single-system is good for newsgathering and home movies, but can cause problems when editing a narrative film. Silent cameras are used when recording sound (onto a synched audio recorder).
in Britain! (i.e. water & electricity not mixing well).
