Part 5/8:
Pioneering efforts in the 1910s, particularly those of Lee de Forest, led to the development of optical sound-on-film technology. Instead of relying on separate media for sound, the film itself contains the audio, represented as jagged lines along its edge. These lines correlate to varying sound amplitudes—a process that allows for direct playback through a projector's optical system.
The projector’s unique sound handling method incorporates an exciter lamp that illuminates the soundtrack. As the film moves, the width of these audio representations alters light transmission through the film, generating electrical signals that are further amplified and outputted as sound.