Audio waveforms printed on the edge of a film print read optically are called?

• A. Analog Sound
• B. Digital Sound
• C. Optical Sound
• D. Magnetic Sound

Answer: (C)

Audio waveforms printed along the edge of a film and read by light is called optical sound. In this system, a narrow optical soundtrack encodes the continuous waveform as variations in light transmission (or density) along the film. During projection, light shines through this track and a photodetector converts the changing light into an electrical signal that drives the speakers. This approach is typically analog, with two common variants—variable-area and variable-density—both conveying the continuous waveform. Magnetic sound would reside on a separate magnetic layer, not read optically, and digital sound would be encoded as discrete digital samples rather than a continuous optical track.