"Eric Archer mods old 8mm cameras to record sound instead of light. He chose vintage movie cameras because of their amazing design, and because the 8mm format fits well with semiconductor light sensors.
He starts by removing the film transport and shutter, leaving just the optics, "My standard modifications include a battery-powered preamp with audio line-out (1/4″ mono jack) + a viewfinder-mounted LED that indicates sensor overload, and a headphone amplifier (1/8″ jack). I’ve prototyped an accessory mount that holds the sound camera steady along side a video camera, focused on the same point for audiovisual recording.
Looking through the viewfinder, you see a normal image. The light sensor’s active region corresponds to a tiny spot in the center of the viewfinder; sweeping the camera across a scene can reveal different sounds, and their source can be pinpointed easily."