Which term is used for the optical readout of audio from a film edge?

• A. Print Master
• B. Optical Sound
• C. PFX
• D. Polywave

Answer: (B)

Optical sound describes the way audio is read from a film edge. The audio track is encoded as a visual strip along the edge whose opacity or density varies with the waveform. As the film runs, light from the projector passes through this track and a photoelectric sensor converts those light variations into an electrical signal, which becomes the sound you hear. This readout method is the standard term for audio on film. The other terms don’t fit: a Print Master is simply the original print used to make copies, and PFX or Polywave aren’t the terms used for the optical readout of film audio.