Info from Legacy Box:
Although most 16mm home movies were shot without sound, there is a way to tell if your film has audio. If your 16mm film has sprockets on both sides, it is a silent film. If it has sprockets on one side and a rust colored strip that runs along the edge of the reel, you have sound! This strip denotes the magnetic portion where the audio is stored and it will run alongside the reel. For the 16mm, the magnetic strip will be on the opposite side of the sprockets.