Std 8mm sound was not very popular as there was only one, rare, std 8mm camera which ever recorded sound - and it used a non-standard spool format. However package movies were available on std 8mm and one could get home movie films striped (or stripe them at home) after development to add a soundtrack. For std 8mm the sound is recorded 56 frames ahead of the picture, making in-camera sound difficult.
For Super 8, circa 1973 Kodak introduced the "Ektasound" system which used enlarged super 8 cartridges with an aperture on the bottom for a pinch roller and sound recording head. The film came pre-striped for sound to be recorded in camera. The super 8 standard had the sound recorded 18 frames ahead of the image, so the film would pass over the recording head at constant speed and then 18 frames later go through the gate with the claw arrangement. Clever, complicated and expensive for the time. But it worked well. Agfa and others produced sound cartridges to this standard too, as it did become quite popular - albeit never as popular as silent cartridges. Having a sound projector was a good idea even if you only shot silent film...because you could buy or rent package movies. Agfa pulled out of super 8 totally in 1992, with Kodak ceasing sound film production around 1997 as the 1970s machines for striping the film were worn out. They were having to reject a lot of film due to defects....and repairing or replacing the machines would have been to costly. by 1997 sound super 8 film was a tiny niche market.
For ingenious home movie makers, prior to "Ektasound",there were dual systems designed to get sound and movies together. Some involved creating a soundtrack on reel to reel tape which was partially synchronised with the 8mm projector. The Eumig P8 Phonomatic projector from the late 50s has a capstan on the side intended to thread reel to reel tape through before it goes back to the tape recorder which does all the recording and playback. You're not going to get "live" synch sound with such a system but could record a commentary with music and perhaps (if you had a portable tape recorder - rare in those days) some "wild" sound from your location. In the 60s the cassette made dual systems more practical and some std 8 and super 8 cameras had sockets which could control a cassette recorder to activate it when the camera was running. Some even had sync signals fed to a dedicated tape recorder which would record mono sound on one track and the sync track on a second track. The cassette and film could then be played back for good synchronised sound. Bulky, as one needed the camera with a cable to a cassette recorder usually worn in a shoulder bag....but it worked. A few people still use this system while some have adapted it to work with digital recorders or even phones as the recording device.
"Ektasound" was much more convenient and Kodak even made 200 foot cartridges which some higher end cameras could take...I last used some in 2004 which were expired but worked OK. Around that time (2000s) some ingenious chap invented a 400 foot system which could have been loaded with bulk length super 8 film and used in any 200' compatible camera but nothing came of it. Probably the wrong time to launch the idea...today there might be more interest than 20 years ago.
The Gaf projector in the link is typical of the mid 70s. Probably decent quality if it works.
