Dean Mullaney & Bruce Canwell, Genius, Isolated: The Life and Art of Alex Toth (San Diego: IDW Publishing, 2011), p. 312.
[Edwin] Gillette produced films for Uncle Sam during the Second World War, earned his film degree from the University of Southern California, and began experimenting with ways to project split-beam images of moving mouths onto otherwise-static pictures of faces to create a “realistic” appearance of speech in the final composite. The result was Gillette’s patented “Synchro-Vox” film technique, which Cambria [Studios] used in the production of Clutch Cargo and subsequent animated series. An uncorroborated story circulating for decades around the fringes of animation suggests that Gillette had a deaf daughter who was unable to read the lips of fully-animated characters; Synchro-Vox was supposedly his attempt to inject real speech into cartoons in order to allow his daughter to enjoy cartoons. Perhaps there is a degree of truth to the story, but Gillette first used the technique to create commercials featuring apparently talking animals, which casts doubts upon its veracity.